IB Physics Terminology

This glossary follows the chapter structure of the IB Physics Guide for first assessment in 2025. It includes core syllabus terminology and additional terms needed to understand formal IB Physics teaching materials. The definitions are written for the IB course context while preserving physical and mathematical accuracy.

Within each syllabus topic, SL and HL contains the common core and AHL contains additional higher level content. Supporting terms are assigned to the earliest level at which they are needed.

Pronunciation conventions

• UK pronunciations use broad phonemic transcription based on General British.
• US pronunciations use broad phonemic transcription based on General American.
• Each entry gives one recommended pronunciation. Some terms also have other accepted regional or individual variants.
• Multi-word terms are transcribed transparently for vocabulary learning. Stress, weak forms and connected speech may vary in complete sentences.
• Slashes indicate broad phonemic transcription. Primary stress is normally omitted for monosyllabic words.

Label	Meaning
UK	British English pronunciation
US	American English pronunciation

A.1 Kinematics

SL and HL

Term	Pronunciation	Definition
acceleration	UK: /əkˌseləˈreɪʃən/ US: /əkˌseləˈreɪʃən/	The rate of change of velocity with time.
air resistance	UK: /eə rɪˈzɪstəns/ US: /er rɪˈzɪstəns/	The resistive force exerted by air on a body moving relative to it.
area under a graph	UK: /ˈeəriə ˈʌndə ə ɡrɑːf/ US: /ˈeriə ˈʌndɚ ə ɡræf/	The signed geometrical area between a graph and its horizontal axis.
average acceleration	UK: /ˈæv.ər.ɪdʒ əkˌseləˈreɪʃən/ US: /ˈæv.ɚ.ɪdʒ əkˌseləˈreɪʃən/	The change in velocity divided by the elapsed time over a specified interval.
average speed	UK: /ˈæv.ər.ɪdʒ spiːd/ US: /ˈæv.ɚ.ɪdʒ spiːd/	Total distance travelled divided by total elapsed time.
average velocity	UK: /ˈæv.ər.ɪdʒ vəˈlɒsɪti/ US: /ˈæv.ɚ.ɪdʒ vəˈlɑːsəti/	Total displacement divided by total elapsed time.
displacement	UK: /dɪˈspleɪs.mənt/ US: /dɪˈspleɪs.mənt/	The vector change in position from the initial point to the final point.
distance travelled	UK: /ˈdɪstəns ˈtrævəld/ US: /ˈdɪstəns ˈtrævəld/	The total length of the path followed by an object.
equations of motion	UK: /ɪˈkweɪʒənz əv ˈməʊʃən/ US: /ɪˈkweɪʒənz əv ˈmoʊʃən/	Equations relating displacement, velocity, acceleration and time; the standard constant-acceleration equations apply only when acceleration is uniform.
fluid resistance	UK: /ˈfluːɪd rɪˈzɪstəns/ US: /ˈfluːɪd rɪˈzɪstəns/	A resistive force exerted by a gas or liquid on a body moving relative to the fluid.
free fall	UK: /friː fɔːl/ US: /friː fɔːl/	Motion under the influence of gravity alone.
gradient	UK: /ˈɡreɪ.di.ənt/ US: /ˈɡreɪ.di.ənt/	The change in the vertical-axis quantity per unit change in the horizontal-axis quantity.
instantaneous velocity	UK: /ˌɪnstənˈteɪniəs vəˈlɒsɪti/ US: /ˌɪnstənˈtæniəs vəˈlɑːsəti/	The instantaneous rate of change of displacement with time.
kinematics	UK: /ˌkɪnɪˈmætɪks/ US: /ˌkɪnəˈmætɪks/	The branch of mechanics that describes motion without referring to the forces that cause it.
light gate	UK: /laɪt ɡeɪt/ US: /laɪt ɡeɪt/	A timing sensor that detects when an object interrupts a light beam, allowing time intervals and speeds to be measured.
motion sensor	UK: /ˈməʊʃən ˈsensə/ US: /ˈmoʊʃən ˈsensɚ/	A sensor that records position or motion as a function of time.
non-uniform acceleration	UK: /ˌnɒn ˈjuːnɪfɔːm əkˌseləˈreɪʃən/ US: /ˌnɑːn ˈjuːnəfɔːrm əkˌseləˈreɪʃən/	Acceleration that changes in magnitude, direction or both with time.
position	UK: /pəˈzɪʃən/ US: /pəˈzɪʃən/	The location of an object relative to a chosen origin.
projectile motion	UK: /prəˈdʒektaɪl ˈməʊʃən/ US: /prəˈdʒektəl ˈmoʊʃən/	Motion after launch under gravity alone, modelled with a uniform gravitational field and negligible air resistance.
range	UK: /reɪndʒ/ US: /reɪndʒ/	The horizontal displacement of a projectile from launch to landing.
reference frame	UK: /ˈrefərəns freɪm/ US: /ˈrefərəns freɪm/	A coordinate system together with synchronized clocks used to assign positions and times to events.
reference point	UK: /ˈrefərəns pɔɪnt/ US: /ˈrefərəns pɔɪnt/	A chosen fixed point relative to which position is measured.
scalar quantity	UK: /ˈskeɪlə ˈkwɒntɪti/ US: /ˈskeɪlər ˈkwɑːntəti/	A physical quantity described by magnitude only.
speed	UK: /spiːd/ US: /spiːd/	The scalar rate at which distance is travelled; equivalently, the magnitude of velocity.
stopwatch	UK: /ˈstɒpwɒtʃ/ US: /ˈstɑːpwɑːtʃ/	An instrument used to measure a time interval.
time of flight	UK: /taɪm əv flaɪt/ US: /taɪm əv flaɪt/	The total time for which a projectile remains in motion before landing.
trajectory	UK: /trəˈdʒektəri/ US: /trəˈdʒektɚi/	The path followed by a moving object.
uniform acceleration	UK: /ˈjuːnɪˌfɔːm əkˌseləˈreɪʃən/ US: /ˈjuːnəˌfɔːrm əkˌseləˈreɪʃən/	Acceleration that remains constant as a vector.
vector quantity	UK: /ˈvektə ˈkwɒntɪti/ US: /ˈvektɚ ˈkwɑːntəti/	A physical quantity described by both magnitude and direction.
velocity	UK: /vəˈlɒsɪti/ US: /vəˈlɑːsəti/	The rate of change of displacement.

A.2 Forces and momentum

SL and HL

Term	Pronunciation	Definition
angular speed	UK: /ˈæŋ.ɡjə.lə spiːd/ US: /ˈæŋ.ɡjə.lɚ spiːd/	The magnitude of angular velocity, equal to the angle swept per unit time.
buoyant force	UK: /ˈbɔɪənt fɔːs/ US: /ˈbɔɪənt fɔːrs/	The resultant force exerted by a fluid on an immersed or partially immersed body, arising from pressure differences.
centripetal acceleration	UK: /ˌsentrɪˈpiːtəl əkˌseləˈreɪʃən/ US: /senˈtrɪpətəl əkˌseləˈreɪʃən/	Acceleration directed towards the centre of a circular path.
centripetal force	UK: /ˌsentrɪˈpiːtəl fɔːs/ US: /senˈtrɪpətəl fɔːrs/	The resultant radial force that produces centripetal acceleration.
coefficient of friction	UK: /ˌkəʊɪˈfɪʃənt əv ˈfrɪkʃən/ US: /ˌkoʊəˈfɪʃənt əv ˈfrɪkʃən/	The dimensionless constant relating frictional force to normal contact force in the stated friction model.
conservation of momentum	UK: /ˌkɒnsəˈveɪʃən əv məˈmentəm/ US: /ˌkɑːnsɚˈveɪʃən əv moʊˈmentəm/	The total momentum of a system remains constant when the resultant external impulse is zero.
contact force	UK: /ˈkɒn.tækt fɔːs/ US: /ˈkɑːn.tækt fɔːrs/	A force arising from direct physical interaction between bodies in contact.
drag force	UK: /dræɡ fɔːs/ US: /dræɡ fɔːrs/	A resistive force exerted by a fluid on an object moving through it.
dynamic friction	UK: /daɪˈnæmɪk ˈfrɪkʃən/ US: /daɪˈnæmɪk ˈfrɪkʃən/	Friction between surfaces that are sliding relative to each other.
elastic collision	UK: /ɪˈlæstɪk kəˈlɪʒən/ US: /ɪˈlæstɪk kəˈlɪʒən/	A collision in an isolated system in which total momentum and total kinetic energy are conserved.
elastic restoring force	UK: /ɪˈlæstɪk rɪˈstɔːrɪŋ fɔːs/ US: /ɪˈlæstɪk rɪˈstɔːrɪŋ fɔːrs/	A force produced by elastic deformation that acts towards the undeformed or equilibrium state.
explosion	UK: /ɪkˈspləʊʒən/ US: /ɪkˈsploʊʒən/	An internal process that separates parts of a system and redistributes energy and momentum.
external force	UK: /ɪkˈstɜːnəl fɔːs/ US: /ɪkˈstɝːnəl fɔːrs/	A force exerted on the chosen system by an object outside that system.
fluid viscosity	UK: /ˈfluːɪd vɪˈskɒsɪti/ US: /ˈfluːɪd vɪˈskɑːsəti/	A measure of a fluid’s resistance to relative motion between adjacent layers; in Stokes’ law it is represented by $\eta$.
force	UK: /fɔːs/ US: /fɔːrs/	A vector quantity describing an interaction that can change a body’s momentum; the resultant force equals the rate of change of momentum.
force pair	UK: /fɔːs peə/ US: /fɔːrs per/	The two equal-magnitude, opposite-direction forces that two interacting bodies exert on each other in accordance with Newton’s third law.
force sensor	UK: /fɔːs ˈsensə/ US: /fɔːrs ˈsensɚ/	A transducer that converts an applied force into a measurable electrical signal.
free-body diagram	UK: /friː ˈbɒdi ˈdaɪəɡræm/ US: /friː ˈbɑːdi ˈdaɪəɡræm/	A diagram showing all external forces acting on one chosen body.
friction	UK: /ˈfrɪkʃən/ US: /ˈfrɪkʃən/	A tangential contact force that opposes relative sliding or the tendency to slide between surfaces.
Hooke’s law	UK: /hʊks lɔː/ US: /hʊks lɔː/	Within the proportional limit, the elastic restoring force is proportional to displacement from equilibrium and acts in the opposite direction, $F_{\mathrm H}=-kx$.
impulse	UK: /ˈɪmpʌls/ US: /ˈɪmpʌls/	The time integral of force; the resultant impulse on a body equals its change in momentum.
inclined plane	UK: /ɪnˈklaɪnd pleɪn/ US: /ɪnˈklaɪnd pleɪn/	A flat surface tilted at an angle to the horizontal.
inelastic collision	UK: /ˌɪnɪˈlæstɪk kəˈlɪʒən/ US: /ˌɪnəˈlæstɪk kəˈlɪʒən/	A collision in which total kinetic energy is not conserved; total momentum is conserved if the external impulse is zero.
inertia	UK: /ɪˈnɜːʃə/ US: /ˌɪˈnɝːʃə/	The property of a body by which it resists a change in velocity; mass is its quantitative measure.
limiting friction	UK: /ˈlɪmɪtɪŋ ˈfrɪkʃən/ US: /ˈlɪmətɪŋ ˈfrɪkʃən/	The maximum possible static friction immediately before slipping begins.
linear momentum	UK: /ˈlɪniə məˈmentəm/ US: /ˈlɪniər moʊˈmentəm/	The product of a body’s mass and velocity, $\boldsymbol{p}=m\boldsymbol{v}$.
mass	UK: /mæs/ US: /mæs/	A scalar measure of a body’s inertia.
momentum	UK: /məˈmentəm/ US: /moʊˈmentəm/	The product of mass and velocity, directed in the same direction as the velocity.
Newton’s first law	UK: /ˈnjuːtənz fɜːst lɔː/ US: /ˈnuːtənz fɝːst lɔː/	An object remains at rest or in uniform straight-line motion unless acted on by a resultant external force.
Newton’s second law	UK: /ˈnjuːtənz ˈsekənd lɔː/ US: /ˈnuːtənz ˈsekənd lɔː/	The resultant force equals the rate of change of momentum; for constant mass, it equals mass times acceleration.
Newton’s third law	UK: /ˈnjuːtənz θɜːd lɔː/ US: /ˈnuːtənz θɝːd lɔː/	When two bodies interact, they exert equal and opposite forces on each other.
normal contact force	UK: /ˈnɔːməl ˈkɒn.tækt fɔːs/ US: /ˈnɔːrməl ˈkɑːn.tækt fɔːrs/	The component of a contact force perpendicular to the contact surface.
perfectly inelastic collision	UK: /ˈpɜːfɪktli ˌɪnɪˈlæstɪk kəˈlɪʒən/ US: /ˈpɝːfɪktli ˌɪnəˈlæstɪk kəˈlɪʒən/	A collision after which the objects move together with a common velocity.
period	UK: /ˈpɪərɪəd/ US: /ˈpɪriəd/	The time taken to complete one full cycle or revolution.
resultant force	UK: /rɪˈzʌltənt fɔːs/ US: /rɪˈzʌltənt fɔːrs/	The vector sum of all forces acting on an object.
spring constant	UK: /ˈsprɪŋ ˌkɒnstənt/ US: /ˈsprɪŋ ˌkɑːnstənt/	The constant of proportionality $k$ between the magnitude of a spring’s restoring force and its displacement from equilibrium within the Hooke’s-law region.
static friction	UK: /ˈstætɪk ˈfrɪkʃən/ US: /ˈstætɪk ˈfrɪkʃən/	Friction between surfaces that are not sliding relative to each other.
surface frictional force	UK: /ˈsɜːfɪs ˈfrɪkʃənəl fɔːs/ US: /ˈsɝːfəs ˈfrɪkʃənəl fɔːrs/	A contact force parallel to the interface that opposes actual or impending relative motion between surfaces.
tension	UK: /ˈtenʃən/ US: /ˈtenʃən/	A pulling force transmitted through a stretched string, rope or cable.
terminal speed	UK: /ˈtɜːmɪnəl spiːd/ US: /ˈtɝːmənəl spiːd/	The constant speed reached when the resultant force is zero and hence acceleration is zero.
uniform circular motion	UK: /ˈjuːnɪˌfɔːm ˈsɜːkjʊlə ˈməʊʃən/ US: /ˈjuːnəˌfɔːrm ˈsɝːkjələr ˈmoʊʃən/	Motion at constant speed along a circular path.
viscous drag force	UK: /ˈvɪskəs dræɡ fɔːs/ US: /ˈvɪskəs dræɡ fɔːrs/	A resistive force caused by motion through a fluid; for a small sphere in the Stokes-law regime, $F_{\mathrm d}=6\pi\eta rv$.
weight	UK: /weɪt/ US: /weɪt/	The gravitational force acting on an object.

A.3 Work, energy and power

SL and HL

Term	Pronunciation	Definition
conservation of energy	UK: /ˌkɒnsəˈveɪʃən əv ˈenədʒi/ US: /ˌkɑːnsɚˈveɪʃən əv ˈenɚdʒi/	The total energy of an isolated system remains constant, although energy may be transferred or transformed.
conservative force	UK: /kənˈsɜːvətɪv fɔːs/ US: /kənˈsɝːvətɪv fɔːrs/	A force whose work between two positions is independent of path; equivalently, its work around any closed path is zero.
dissipation	UK: /ˌdɪsɪˈpeɪʃən/ US: /ˌdɪsɪˈpeɪʃən/	The transfer of energy into the internal energy of a system and its surroundings, making that energy less available for useful mechanical work while total energy remains conserved.
efficiency	UK: /ɪˈfɪʃənsi/ US: /ɪˈfɪʃənsi/	The ratio of useful work out to total work in, equivalently useful power out to total power in.
elastic potential energy	UK: /ɪˈlæstɪk pəˈtenʃəl ˈenədʒi/ US: /ɪˈlæstɪk pəˈtenʃəl ˈenɚdʒi/	Energy stored by elastic deformation; for a spring obeying Hooke’s law, $E_{\mathrm H}=\frac{1}{2}k(\Delta x)^2$.
energy	UK: /ˈenədʒi/ US: /ˈenɚdʒi/	A conserved scalar property of a system that can be transferred between systems or transformed between forms.
energy density of a fuel	UK: /ˈenədʒi ˈdensɪti əv ə ˈfjuːəl/ US: /ˈenɚdʒi ˈdensəti əv ə ˈfjuːəl/	The energy released per unit mass of fuel, expressed in $\mathrm{J\,kg^{-1}}$.
energy transfer	UK: /ˈenədʒi ˈtrænsfɜː/ US: /ˈenɚdʒi ˈtrænsfɝː/	The movement of energy from one system or part of a system to another, for example by work, heating or radiation.
gravitational potential energy	UK: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl ˈenədʒi/ US: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl ˈenɚdʒi/	The energy of a system due to the relative positions of its masses.
kinetic energy	UK: /kɪˈnetɪk ˈenədʒi/ US: /kɪˈnetɪk ˈenɚdʒi/	The energy of a body due to its motion, $E_{\mathrm k}=\frac{1}{2}mv^2=\frac{p^2}{2m}$.
mechanical energy	UK: /mɪˈkænɪkəl ˈenədʒi/ US: /məˈkænɪkəl ˈenɚdʒi/	The sum of the kinetic energies and the relevant potential energies of a mechanical system.
non-conservative force	UK: /ˌnɒn kənˈsɜːvətɪv fɔːs/ US: /ˌnɑːn kənˈsɝːvətɪv fɔːrs/	A force for which the work done depends on the path taken, so its work can change the mechanical energy of a system.
power	UK: /paʊə/ US: /ˈpaʊ.ɚ/	The rate at which work is done or energy is transferred.
Sankey diagram	UK: /ˈsæŋki ˈdaɪəɡræm/ US: /ˈsæŋki ˈdaɪəɡræm/	A diagram of energy transfers in which arrow widths are proportional to the corresponding energies or powers.
system	UK: /ˈsɪstəm/ US: /ˈsɪstəm/	The object or collection of objects selected for analysis.
useful power output	UK: /ˈjuːsfəl ˈpaʊə ˈaʊtpʊt/ US: /ˈjuːsfəl ˈpaʊɚ ˈaʊtpʊt/	The rate at which a device transfers energy by the intended useful pathway.
work	UK: /wɜːk/ US: /wɝːk/	Energy transferred by a force when its point of application moves.
work done	UK: /wɜːk dʌn/ US: /wɝːk dʌn/	For a constant force, the scalar product of force and displacement; more generally, the integral of force along the path.
work-energy theorem	UK: /wɜːk ˈenədʒi ˈθɪərəm/ US: /wɝːk ˈenɚdʒi ˈθɪrəm/	The resultant work done on an object equals its change in kinetic energy.

A.4 Rigid body mechanics

AHL

Term	Pronunciation	Definition
angular acceleration	UK: /ˈæŋ.ɡjə.lə əkˌseləˈreɪʃən/ US: /ˈæŋ.ɡjə.lɚ əkˌseləˈreɪʃən/	The rate of change of angular velocity with time.
angular displacement	UK: /ˈæŋ.ɡjə.lə dɪˈspleɪs.mənt/ US: /ˈæŋ.ɡjə.lɚ dɪˈspleɪs.mənt/	The angle through which a body rotates, with a specified sense.
angular impulse	UK: /ˈæŋ.ɡjə.lə ˈɪmpʌls/ US: /ˈæŋ.ɡjə.lɚ ˈɪmpʌls/	The product of average resultant torque and the time interval for which it acts, equal to the change in angular momentum.
angular momentum	UK: /ˈæŋ.ɡjə.lə məˈmentəm/ US: /ˈæŋ.ɡjə.lɚ moʊˈmentəm/	The rotational analogue of linear momentum; for a rigid body rotating about a fixed axis, $L=I\omega$.
angular position	UK: /ˈæŋ.ɡjə.lə pəˈzɪʃən/ US: /ˈæŋ.ɡjə.lɚ pəˈzɪʃən/	The orientation of a body relative to a chosen angular reference.
angular velocity	UK: /ˈæŋ.ɡjə.lə vəˈlɒsɪti/ US: /ˈæŋ.ɡjə.lɚ vəˈlɑːsəti/	The rate of change of angular displacement with time, including the sense of rotation.
average torque	UK: /ˈæv.ər.ɪdʒ tɔːk/ US: /ˈæv.ɚ.ɪdʒ tɔːrk/	The angular impulse delivered during a time interval divided by that interval.
axis of rotation	UK: /ˈæk.sɪs əv rəʊˈteɪʃən/ US: /ˈæk.sɪs əv roʊˈteɪʃən/	The line about which a body rotates.
axle	UK: /ˈæksəl/ US: /ˈæksəl/	A shaft about which a wheel, pulley or other body rotates.
centre of mass	UK: /ˈsentə əv mæs/ US: /ˈsentɚ əv mæs/	The point at which the mass of an extended body may be considered concentrated when analysing its translational motion.
conservation of angular momentum	UK: /ˌkɒnsəˈveɪʃən əv ˈæŋ.ɡjə.lə məˈmentəm/ US: /ˌkɑːnsɚˈveɪʃən əv ˈæŋ.ɡjə.lɚ moʊˈmentəm/	Total angular momentum remains constant when resultant external torque is zero.
equations of rotational motion	UK: /ɪˈkweɪʒənz əv rəʊˈteɪʃənəl ˈməʊʃən/ US: /ɪˈkweɪʒənz əv roʊˈteɪʃənəl ˈmoʊʃən/	Equations relating angular displacement, angular velocity, angular acceleration and time; the standard forms apply only when angular acceleration is uniform.
line of action	UK: /laɪn əv ˈækʃən/ US: /laɪn əv ˈækʃən/	The infinite straight line along which a force acts.
moment arm	UK: /ˈməʊmənt ɑːm/ US: /ˈmoʊmənt ɑːrm/	The perpendicular distance from the axis to the line of action of a force.
moment of inertia	UK: /ˈməʊmənt əv ɪˈnɜːʃə/ US: /ˈmoʊmənt əv ˌɪˈnɝːʃə/	The rotational inertia of a body about a specified axis, defined for point masses by $I=\sum mr^2$, where $r$ is the perpendicular distance from the axis.
pulley	UK: /ˈpʊli/ US: /ˈpʊli/	A wheel over which a string or belt passes; if its rotational inertia is not negligible, the tensions on its two sides need not be equal.
pure rolling	UK: /pjʊə ˈrəʊlɪŋ/ US: /pjʊr ˈroʊlɪŋ/	Another term for rolling without slipping.
resultant torque	UK: /rɪˈzʌltənt tɔːk/ US: /rɪˈzʌltənt tɔːrk/	The signed sum, about a specified axis, of all torques acting on a body.
rigid body	UK: /ˈrɪdʒɪd ˈbɒdi/ US: /ˈrɪdʒəd ˈbɑːdi/	An idealized body whose shape and dimensions do not change.
rolling without slipping	UK: /ˈrəʊlɪŋ wɪˈðaʊt ˈslɪpɪŋ/ US: /ˈroʊlɪŋ wɪˈθaʊt ˈslɪpɪŋ/	Combined translation and rotation with no relative motion at the contact point.
rotational equilibrium	UK: /rəʊˈteɪʃənəl ˌiːkwɪˈlɪbrɪəm/ US: /roʊˈteɪʃənəl ˌiːkwəˈlɪbriəm/	A state in which the resultant torque is zero.
rotational kinetic energy	UK: /rəʊˈteɪʃənəl kɪˈnetɪk ˈenədʒi/ US: /roʊˈteɪʃənəl kɪˈnetɪk ˈenɚdʒi/	The kinetic energy of a rigid body rotating about a fixed axis, $E_{\mathrm k}=\frac{1}{2}I\omega^2=\frac{L^2}{2I}$.
rotational motion	UK: /rəʊˈteɪʃənəl ˈməʊʃən/ US: /roʊˈteɪʃənəl ˈmoʊʃən/	Motion of a body about an axis.
static equilibrium	UK: /ˈstætɪk ˌiːkwɪˈlɪbrɪəm/ US: /ˈstætɪk ˌiːkwəˈlɪbriəm/	A state in which a body is at rest and both the resultant force and resultant torque are zero.
torque	UK: /tɔːk/ US: /tɔːrk/	The turning effect of a force about an axis; its magnitude is $\tau=Fr\sin\theta$, where $r$ is the distance from the axis and $\theta$ is the angle between the force and the radial direction.
translational equilibrium	UK: /trænˈsleɪʃənəl ˌiːkwɪˈlɪbrɪəm/ US: /trænzˈleɪʃənəl ˌiːkwəˈlɪbriəm/	A state in which the resultant force is zero.
translational motion	UK: /trænˈsleɪʃənəl ˈməʊʃən/ US: /trænzˈleɪʃənəl ˈmoʊʃən/	Motion in which every point of a body has the same displacement.

A.5 Galilean and special relativity

AHL

Term	Pronunciation	Definition
event	UK: /ɪˈvent/ US: /ɪˈvent/	Something that occurs at one position and one instant.
Galilean relativity	UK: /ˌɡælɪˈleɪən rɪləˈtɪvɪti/ US: /ˌɡælɪˈliːən ˌreləˈtɪvəti/	The principle that Newtonian mechanics has the same form in all inertial frames.
Galilean transformation	UK: /ˌɡælɪˈleɪən ˌtrænsfəˈmeɪʃən/ US: /ˌɡælɪˈliːən ˌtrænsfɚˈmeɪʃən/	The classical equations relating event coordinates in uniformly moving frames.
inertial reference frame	UK: /ɪˈnɜːʃəl ˈrefərəns freɪm/ US: /ˌɪˈnɝːʃəl ˈrefərəns freɪm/	A reference frame in which a free body has constant velocity and Newton’s first law holds.
invariant quantity	UK: /ɪnˈveəriənt ˈkwɒntɪti/ US: /ˌɪnˈveriənt ˈkwɑːntəti/	A quantity that has the same value in all relevant reference frames.
length contraction	UK: /leŋθ kənˈtrækʃən/ US: /leŋkθ kənˈtrækʃən/	The measured length of an object parallel to relative motion is shorter than its proper length.
Lorentz factor	UK: /ˈlɒrənts ˈfæktə/ US: /ˈlɔːrents ˈfæktɚ/	The factor that determines the size of relativistic effects at a given relative speed.
Lorentz transformation	UK: /ˈlɒrənts ˌtrænsfəˈmeɪʃən/ US: /ˈlɔːrents ˌtrænsfɚˈmeɪʃən/	The relativistic equations relating space and time coordinates in inertial frames.
low-speed limit	UK: /ləʊ spiːd ˈlɪmɪt/ US: /loʊ spiːd ˈlɪmət/	The regime $v\ll c$ in which relativistic predictions approach the corresponding classical results.
muon decay	UK: /ˈmjuːɒn dɪˈkeɪ/ US: /ˈmjuːɑːn dɪˈkeɪ/	The spontaneous transformation of a muon into lighter particles.
observer	UK: /əbˈzɜːvə/ US: /əbˈzɝːvɚ/	An idealized measurer at rest in a specified reference frame who assigns coordinates and times to events.
postulate	UK: /ˈpɒstʃələt/ US: /ˈpɑːstʃələt/	A fundamental assumption adopted as a basis of a theory.
proper length	UK: /ˈprɒpə leŋθ/ US: /ˈprɑːpɚ leŋkθ/	The length of an object measured simultaneously in the object’s rest frame.
proper time	UK: /ˈprɒpə taɪm/ US: /ˈprɑːpɚ taɪm/	The time interval between two events measured by a single clock present at both events.
reference frame	UK: /ˈrefərəns freɪm/ US: /ˈrefərəns freɪm/	A coordinate system together with synchronized clocks used to assign positions and times to events.
relativistic velocity addition	UK: /ˌrelətɪˈvɪstɪk vəˈlɒsɪti əˈdɪʃən/ US: /ˌrelətɪˈvɪstɪk vəˈlɑːsəti əˈdɪʃən/	The velocity transformation consistent with an invariant speed of light.
relativity of simultaneity	UK: /rɪləˈtɪvɪti əv ˌsɪməlˈteɪnɪti/ US: /ˌreləˈtɪvəti əv ˌsaɪməltəˈniːəti/	The dependence of simultaneity of separated events on the observer’s frame.
rest frame	UK: /rest freɪm/ US: /rest freɪm/	A frame in which a specified object is at rest.
simultaneous events	UK: /ˌsɪməlˈteɪniəs ɪˈvents/ US: /ˌsaɪməlˈteɪniəs ɪˈvents/	Events assigned the same time coordinate in a specified reference frame.
space axis	UK: /speɪs ˈæk.sɪs/ US: /speɪs ˈæk.sɪs/	An axis on a space-time diagram representing position in the chosen inertial reference frame, conventionally labelled $x$ or $x'$.
space-time diagram	UK: /speɪs taɪm ˈdaɪəɡræm/ US: /speɪs taɪm ˈdaɪəɡræm/	A diagram representing position and time coordinates of events.
space-time interval	UK: /speɪs taɪm ˈɪntəvəl/ US: /speɪs taɪm ˈɪntɚvəl/	The invariant separation of two events; in one spatial dimension, $(\Delta s)^2=(c\Delta t)^2-\Delta x^2$.
special relativity	UK: /ˈspeʃəl rɪləˈtɪvɪti/ US: /ˈspeʃəl ˌreləˈtɪvəti/	The theory based on the equivalence of inertial frames and the invariance of the speed of light in vacuum.
speed of light	UK: /spiːd əv laɪt/ US: /spiːd əv laɪt/	The invariant speed of electromagnetic radiation in vacuum.
time axis	UK: /taɪm ˈæk.sɪs/ US: /taɪm ˈæk.sɪs/	An axis on a space-time diagram representing time multiplied by the speed of light, conventionally labelled $ct$ or $ct'$.
time dilation	UK: /taɪm daɪˈleɪʃən/ US: /taɪm ˌdaɪˈleɪʃən/	The relation by which the time interval between two events is greater in a frame where they occur at different positions than the proper time.
velocity addition	UK: /vəˈlɒsɪti əˈdɪʃən/ US: /vəˈlɑːsəti əˈdɪʃən/	A relation connecting the velocity of an object measured in different frames.
world line	UK: /wɜːld laɪn/ US: /wɝːld laɪn/	The path of an object through space-time.

B.1 Thermal energy transfers

SL and HL

Term	Pronunciation	Definition
absolute zero	UK: /ˈæbsəˌluːt ˈzɪərəʊ/ US: /ˈæbsəˌluːt ˈzɪroʊ/	The zero of thermodynamic temperature, equal to 0 K or −273.15 °C.
apparent brightness	UK: /əˈpærənt ˈbraɪtnəs/ US: /əˈperənt ˈbraɪtnəs/	The radiant power received per unit area from an astronomical source.
average kinetic energy	UK: /ˈæv.ər.ɪdʒ kɪˈnetɪk ˈenədʒi/ US: /ˈæv.ɚ.ɪdʒ kɪˈnetɪk ˈenɚdʒi/	The arithmetic mean of the kinetic energies of the particles in a system; for an ideal monatomic gas it is proportional to absolute temperature.
black body	UK: /blæk ˈbɒdi/ US: /blæk ˈbɑːdi/	An ideal body that absorbs all incident electromagnetic radiation and, at a given temperature, emits the maximum possible thermal radiation.
black-body spectrum	UK: /blæk ˈbɒdi ˈspektrəm/ US: /blæk ˈbɑːdi ˈspektrəm/	The continuous distribution of electromagnetic radiation emitted by an ideal black body as a function of wavelength or frequency.
boiling	UK: /ˈbɔɪlɪŋ/ US: /ˈbɔɪlɪŋ/	Vaporization throughout a liquid at its boiling temperature.
calorimeter	UK: /ˌkæləˈrɪmɪtə/ US: /ˌkæləˈrɪmətɚ/	An insulated apparatus used to measure thermal energy transfers from temperature or phase changes.
Celsius scale	UK: /ˈselsiəs skeɪl/ US: /ˈselsiəs skeɪl/	A temperature scale whose degree has the same size as the kelvin and for which 0 °C corresponds to 273.15 K.
condensation	UK: /kɒndɪnˈseɪʃən/ US: /ˌkɑːndənˈseɪʃən/	The change from gas to liquid.
conduction	UK: /kənˈdʌkʃən/ US: /kənˈdʌkʃən/	Thermal energy transfer through microscopic particle interactions, without bulk transport of matter.
convection	UK: /kənˈvekʃən/ US: /kənˈvekʃən/	Thermal energy transfer by the bulk motion of a fluid.
density	UK: /ˈdensɪti/ US: /ˈdensəti/	Mass per unit volume.
evaporation	UK: /ɪˌvæpəˈreɪʃən/ US: /ɪˌvæpɚˈeɪʃən/	Vaporization from the surface of a liquid below or at its boiling point.
freezing	UK: /ˈfriːzɪŋ/ US: /ˈfriːzɪŋ/	The change from liquid to solid.
gas	UK: /ɡæs/ US: /ɡæs/	A state of matter with neither fixed shape nor fixed volume.
heat capacity	UK: /hiːt kəˈpæsɪti/ US: /hiːt kəˈpæsəti/	The thermal energy required to raise the temperature of a whole body by one kelvin, under stated conditions.
intermolecular potential energy	UK: /ˌɪntəməˈlek.jə.lə pəˈtenʃəl ˈenədʒi/ US: /ˌɪntərməˈlek.jə.lɚ pəˈtenʃəl ˈenɚdʒi/	Potential energy associated with the relative positions of molecules and the forces between them.
internal energy	UK: /ɪnˈtɜːnəl ˈenədʒi/ US: /ˌɪnˈtɝːnəl ˈenɚdʒi/	The sum of the random kinetic energies of the particles in a system and the potential energies associated with their interactions.
Kelvin scale	UK: /ˈkel.vɪn skeɪl/ US: /ˈkel.vɪn skeɪl/	The absolute thermodynamic temperature scale, with zero kelvin at absolute zero.
liquid	UK: /ˈlɪkwɪd/ US: /ˈlɪkwəd/	A state of matter with fixed volume but no fixed shape.
luminosity	UK: /ˌluːmɪˈnɒsɪti/ US: /ˌluːməˈnɑːsəti/	The total power radiated by a body.
melting	UK: /ˈmeltɪŋ/ US: /ˈmeltɪŋ/	The change from solid to liquid.
molecular theory	UK: /məˈlek.jə.lə ˈθɪəri/ US: /məˈlek.jə.lɚ ˈθɪri/	A model that explains macroscopic properties of matter in terms of the arrangement, motion and interactions of molecules.
particle model	UK: /ˈpɑːtɪkəl ˈmɒdəl/ US: /ˈpɑːrtəkəl ˈmɑːdəl/	A model that explains matter in terms of moving and interacting particles.
peak wavelength	UK: /piːk ˈweɪv.leŋθ/ US: /piːk ˈweɪv.leŋθ/	The wavelength at which a spectrum has its maximum spectral intensity; for a black body it obeys Wien’s displacement law.
phase change	UK: /feɪz tʃeɪndʒ/ US: /feɪz tʃeɪndʒ/	A change of state involving a change in particle behaviour and energy while temperature remains constant under the stated conditions.
random kinetic energy	UK: /ˈrændəm kɪˈnetɪk ˈenədʒi/ US: /ˈrændəm kɪˈnetɪk ˈenɚdʒi/	The kinetic energy associated with the disordered microscopic motion of particles in a system.
solid	UK: /ˈsɒlɪd/ US: /ˈsɑːləd/	A state of matter with fixed volume and shape under ordinary conditions.
specific heat capacity	UK: /spəˈsɪf.ɪk hiːt kəˈpæsɪti/ US: /spəˈsɪf.ɪk hiːt kəˈpæsəti/	The energy required per unit mass to raise a substance’s temperature by one kelvin, without a change of state.
specific latent heat	UK: /spəˈsɪf.ɪk ˈleɪtənt hiːt/ US: /spəˈsɪf.ɪk ˈleɪtənt hiːt/	The energy transferred per unit mass during a specified change of state at constant temperature.
specific latent heat of fusion	UK: /spəˈsɪf.ɪk ˈleɪtənt hiːt əv ˈfjuːʒən/ US: /spəˈsɪf.ɪk ˈleɪtənt hiːt əv ˈfjuːʒən/	The energy transferred per unit mass to change a substance between solid and liquid at constant temperature.
specific latent heat of vaporization	UK: /spəˈsɪf.ɪk ˈleɪtənt hiːt əv ˌveɪpəraɪˈzeɪʃən/ US: /spəˈsɪf.ɪk ˈleɪtənt hiːt əv ˌveɪpərəˈzeɪʃən/	The energy transferred per unit mass to change a substance between liquid and gas at constant temperature.
Stefan-Boltzmann law	UK: /ˈstefən ˈbɒltsmən lɔː/ US: /ˈstefən ˈboʊltsmən lɔː/	The law relating black-body luminosity to area and the fourth power of temperature.
temperature	UK: /ˈtemprətʃə/ US: /ˈtemprətʃɚ/	A thermodynamic state quantity that determines the direction of net thermal energy transfer; for an ideal gas it is proportional to mean translational kinetic energy.
temperature gradient	UK: /ˈtemprətʃə ˈɡreɪ.di.ənt/ US: /ˈtemprətʃɚ ˈɡreɪ.di.ənt/	The signed change in temperature per unit distance; thermal energy transfer by conduction is directed opposite to this gradient.
thermal conductivity	UK: /ˈθɜːməl kɒndʌkˈtɪvɪti/ US: /ˈθɝːməl ˌkɑːnˌdʌkˈtɪvəti/	A material property measuring its ability to conduct thermal energy.
thermal energy transfer	UK: /ˈθɜːməl ˈenədʒi ˈtrænsfɜː/ US: /ˈθɝːməl ˈenɚdʒi ˈtrænsfɝː/	Energy transferred because of a temperature difference or by a thermal-transfer mechanism such as conduction, convection or radiation.
thermal equilibrium	UK: /ˈθɜːməl ˌiːkwɪˈlɪbrɪəm/ US: /ˈθɝːməl ˌiːkwəˈlɪbriəm/	A state in which systems in thermal contact have no net energy transfer between them by heating.
thermal insulation	UK: /ˈθɜːməl ˌɪnsjʊˈleɪʃən/ US: /ˈθɝːməl ˌɪnsəˈleɪʃən/	Material or an arrangement used to reduce thermal energy transfer between a system and its surroundings.
thermal radiation	UK: /ˈθɜːməl ˌreɪdɪˈeɪʃən/ US: /ˈθɝːməl ˌreɪdiˈeɪʃən/	Electromagnetic radiation emitted by matter because of its temperature, transferring energy without requiring a material medium.
thermocouple	UK: /ˈθɜːməʊkʌpəl/ US: /ˈθɝːmoʊkʌpəl/	A temperature sensor that produces an emf related to the temperature difference between junctions of dissimilar conductors.
thermometer	UK: /θəˈmɒmɪtə/ US: /θɚˈmɑːmətɚ/	An instrument used to measure temperature through a calibrated temperature-dependent property.
Wien’s displacement law	UK: /viːnz dɪˈspleɪs.mənt lɔː/ US: /viːnz dɪˈspleɪs.mənt lɔː/	The law relating a black body’s peak wavelength to its temperature.

B.2 Greenhouse effect

SL and HL

Term	Pronunciation	Definition
absorption	UK: /əbˈzɔːpʃən/ US: /əbˈzɔːrpʃən/	The transfer of radiation energy into matter.
albedo	UK: /ælˈbiːdəʊ/ US: /ælˈbiːdoʊ/	The ratio of total scattered radiant power to total incident radiant power for a surface or macroscopic system.
black surface	UK: /blæk ˈsɜːfɪs/ US: /blæk ˈsɝːfəs/	An ideal surface that absorbs all incident electromagnetic radiation and has emissivity equal to one.
carbon dioxide	UK: /ˈkɑːbən daɪˈɒkˌsaɪd/ US: /ˈkɑːrbən daɪˈɑːkˌsaɪd/	A greenhouse gas whose atmospheric concentration is increased by fossil-fuel combustion.
climate feedback	UK: /ˈklaɪmɪt ˈfiːdˌbæk/ US: /ˈklaɪmət ˈfiːdˌbæk/	A process that amplifies or reduces an initial climate change.
emission	UK: /ɪˈmɪʃən/ US: /ɪˈmɪʃən/	The release of electromagnetic radiation by matter.
emissivity	UK: /ˌemɪˈsɪvəti/ US: /ˌemɪˈsɪvəti/	At a stated wavelength or over a stated spectrum, the ratio of a surface’s emitted radiative power to that of an ideal black body at the same temperature and area.
energy balance	UK: /ˈenədʒi ˈbæləns/ US: /ˈenɚdʒi ˈbæləns/	An accounting of energy entering, leaving and being stored in a system.
enhanced greenhouse effect	UK: /ɪnˈhɑːnst ˈɡriːnˌhaʊs ɪˈfekt/ US: /enˈhænst ˈɡriːnˌhaʊs ɪˈfekt/	Additional warming caused by increased greenhouse-gas concentrations.
fossil fuel	UK: /ˈfɒsəl ˈfjuːəl/ US: /ˈfɑːsəl ˈfjuːəl/	A carbon-containing fuel formed from ancient biological material; its combustion is a major anthropogenic source of greenhouse gases.
greenhouse effect	UK: /ˈɡriːnˌhaʊs ɪˈfekt/ US: /ˈɡriːnˌhaʊs ɪˈfekt/	The warming of a planet’s surface and lower atmosphere because the atmosphere absorbs and re-emits outgoing infrared radiation.
greenhouse gas	UK: /ˈɡriːnˌhaʊs ɡæs/ US: /ˈɡriːnˌhaʊs ɡæs/	An atmospheric gas that absorbs and emits infrared radiation at relevant wavelengths.
incident power	UK: /ˈɪn.sɪ.dənt ˈpaʊə/ US: /ˈɪn.sɪ.dənt ˈpaʊər/	The rate at which radiant energy arrives at a surface or system.
infrared radiation	UK: /ˌɪnfrəˈred ˌreɪdɪˈeɪʃən/ US: /ˌɪnfrɚˈed ˌreɪdiˈeɪʃən/	Electromagnetic radiation with wavelengths longer than visible light.
methane	UK: /ˈmiːθeɪn/ US: /ˈmeθeɪn/	The greenhouse gas $\mathrm{CH_4}$, which absorbs and emits infrared radiation in particular wavelength bands.
natural greenhouse effect	UK: /ˈnætʃ.ər.əl ˈɡriːnˌhaʊs ɪˈfekt/ US: /ˈnætʃ.ɚ.əl ˈɡriːnˌhaʊs ɪˈfekt/	The greenhouse warming that occurs naturally in a planetary atmosphere.
nitrous oxide	UK: /ˈnaɪtrəs ˈɒksaɪd/ US: /ˈnaɪtrəs ˈɑːksaɪd/	The greenhouse gas $\mathrm{N_2O}$, with both natural and human-related sources.
projected surface	UK: /prəˈdʒektɪd ˈsɜːfɪs/ US: /prəˈdʒektɪd ˈsɝːfəs/	The apparent area of a surface perpendicular to the direction of incident rays, used to determine intercepted radiative power.
radiative equilibrium	UK: /ˈreɪdiətɪv ˌiːkwɪˈlɪbrɪəm/ US: /ˈreɪdiətɪv ˌiːkwəˈlɪbriəm/	A state in which absorbed and emitted radiative powers are balanced.
radiative forcing	UK: /ˈreɪdiətɪv ˈfɔːsɪŋ/ US: /ˈreɪdiətɪv ˈfɔːrsɪŋ/	A change in the net radiative energy flux of a climate system.
re-emission	UK: /ˌriːɪˈmɪʃən/ US: /ˌriːɪˈmɪʃən/	The emission of energy after it has previously been absorbed.
resonance model	UK: /ˈrezənəns ˈmɒdəl/ US: /ˈrezənəns ˈmɑːdəl/	A model in which greenhouse-gas molecules absorb infrared radiation when its frequency matches an allowed molecular mode or transition.
scattered power	UK: /ˈskætəd ˈpaʊə/ US: /ˈskætərd ˈpaʊər/	The rate at which incident radiant energy is redirected away from a surface or system.
solar constant	UK: /ˈsəʊlə ˈkɒnstənt/ US: /ˈsoʊlɚ ˈkɑːnstənt/	The solar radiant power received per unit area normal to the Sun’s rays at Earth’s mean orbital distance.
water vapour	UK: /ˈwɔːtə ˈveɪpə/ US: /ˈwɔːtɚ ˈveɪpɚ/	Water in the gas phase, an important naturally occurring greenhouse gas.

B.3 Gas laws

SL and HL

Term	Pronunciation	Definition
absolute temperature	UK: /ˈæbsəˌluːt ˈtemprətʃə/ US: /ˈæbsəˌluːt ˈtemprətʃɚ/	Thermodynamic temperature measured from absolute zero.
amount of substance	UK: /əˈmaʊnt əv ˈsʌbstəns/ US: /əˈmaʊnt əv ˈsʌbstəns/	The number of specified elementary entities divided by the Avogadro constant, $n=N/N_{\mathrm A}$, measured in moles.
Avogadro constant	UK: /ˌævəˈɡɑːdrəʊ ˈkɒnstənt/ US: /ˌɑːvəˈɡɑːdroʊ ˈkɑːnstənt/	The exact number of specified elementary entities per mole, $6.02214076\times10^{23}\ \mathrm{mol^{-1}}$.
Boltzmann constant	UK: /ˈbɒltsmən ˈkɒnstənt/ US: /ˈboʊltsmən ˈkɑːnstənt/	The constant $k_{\mathrm B}$ relating absolute temperature to energy on the particle scale.
Boyle’s law	UK: /bɔɪlz lɔː/ US: /bɔɪlz lɔː/	For fixed temperature and amount of gas, pressure is inversely proportional to volume.
Charles’s law	UK: /ˈtʃɑːlzɪz lɔː/ US: /ˈtʃɑːrlzɪz lɔː/	For fixed pressure and amount of gas, volume is proportional to absolute temperature.
elastic collision	UK: /ɪˈlæstɪk kəˈlɪʒən/ US: /ɪˈlæstɪk kəˈlɪʒən/	A collision in an isolated system in which total momentum and total kinetic energy are conserved.
equation of state	UK: /ɪˈkweɪʒən əv steɪt/ US: /ɪˈkweɪʒən əv steɪt/	A relation connecting pressure, volume, temperature and amount of gas.
gas cylinder	UK: /ɡæs ˈsɪlɪndə/ US: /ɡæs ˈsɪləndɚ/	A rigid cylindrical container used to hold a gas, often at a pressure different from atmospheric pressure.
gas syringe	UK: /ɡæs sɪˈrɪndʒ/ US: /ɡæs sɪˈrɪndʒ/	A graduated cylinder with a movable plunger used to contain and measure a gas volume.
ideal gas	UK: /aɪˈdiː.əl ɡæs/ US: /aɪˈdiː.əl ɡæs/	A model gas of particles with negligible volume, no intermolecular forces except during collisions, and perfectly elastic collisions.
ideal gas law	UK: /aɪˈdiː.əl ɡæs lɔː/ US: /aɪˈdiː.əl ɡæs lɔː/	The equation relating pressure, volume, amount of substance and absolute temperature for an ideal gas.
kinetic theory	UK: /kɪˈnetɪk ˈθɪəri/ US: /kɪˈnetɪk ˈθɪri/	A microscopic theory that explains the macroscopic behaviour of gases in terms of particle motion and collisions.
manometer	UK: /məˈnɒmɪtə/ US: /məˈnɑːmətɚ/	An instrument that determines a pressure or pressure difference, often from the height difference of liquid columns.
mean square speed	UK: /miːn skweə spiːd/ US: /miːn skwer spiːd/	The average of the squares of particle speeds in a gas.
microscopic model	UK: /ˌmaɪkrəˈskɒpɪk ˈmɒdəl/ US: /ˌmaɪkrəˈskɑːpɪk ˈmɑːdəl/	A model describing macroscopic behaviour in terms of particles and their interactions.
molar gas constant	UK: /ˈməʊlə ɡæs ˈkɒnstənt/ US: /ˈmoʊlɚ ɡæs ˈkɑːnstənt/	The constant $R$ in the molar ideal-gas equation $PV=nRT$, equal to $N_{\mathrm A}k_{\mathrm B}$.
molar mass	UK: /ˈməʊlə mæs/ US: /ˈmoʊlər mæs/	The mass of a substance divided by its amount of substance.
mole	UK: /məʊl/ US: /moʊl/	The amount of substance containing exactly $6.02214076\times10^{23}$ specified elementary entities.
molecular collision	UK: /məˈlek.jə.lə kəˈlɪʒən/ US: /məˈlek.jə.lɚ kəˈlɪʒən/	An interaction in which gas particles exchange momentum and energy.
monatomic ideal gas	UK: /ˌmɒnəˈtɒmɪk aɪˈdiː.əl ɡæs/ US: /ˌmɑːnəˈtɑːmɪk aɪˈdiː.əl ɡæs/	An ideal gas whose particles are single atoms and whose internal energy is modelled as translational kinetic energy only.
number of molecules	UK: /ˈnʌmbə əv ˈmɒlɪkjuːlz/ US: /ˈnʌmbər əv ˈmɑːlɪkjuːlz/	The count $N$ of molecules in a sample, related to amount of substance by $N=nN_{\mathrm A}$.
piston	UK: /ˈpɪstən/ US: /ˈpɪstən/	A movable, close-fitting component in a cylinder that can change the volume of an enclosed gas and transmit force.
pressure	UK: /ˈpreʃə/ US: /ˈpreʃɚ/	The normal force exerted per unit area.
pressure gauge	UK: /ˈpreʃə ɡeɪdʒ/ US: /ˈpreʃɚ ɡeɪdʒ/	An instrument used to measure pressure, often relative to atmospheric pressure.
pressure law	UK: /ˈpreʃə lɔː/ US: /ˈpreʃɚ lɔː/	For fixed volume and amount of gas, pressure is proportional to absolute temperature.
pressure sensor	UK: /ˈpreʃə ˈsensə/ US: /ˈpreʃɚ ˈsensɚ/	A transducer that converts pressure into a measurable signal.
real gas	UK: /rɪəl ɡæs/ US: /ˈriːəl ɡæs/	A gas whose particles have finite volume and intermolecular interactions, so it may depart from the ideal-gas model.
root-mean-square speed	UK: /ruːt miːn skweə spiːd/ US: /ruːt miːn skwer spiːd/	The square root of the mean square speed.

B.4 Thermodynamics

AHL

Term	Pronunciation	Definition
adiabatic process	UK: /ˌeɪdiəˈbætɪk ˈprəʊses/ US: /ˌeɪdiəˈbætɪk ˈprɑːses/	A thermodynamic process in which no energy is transferred by heating between the system and its surroundings.
boundary	UK: /ˈbaʊndri/ US: /ˈbaʊndɚi/	The real or imaginary surface separating a system from its surroundings.
Carnot cycle	UK: /ˈkɑːnəʊ ˈsaɪkəl/ US: /kɑːrˈnoʊ ˈsaɪkəl/	An ideal reversible cycle operating between two thermal reservoirs that sets the maximum possible efficiency for those reservoir temperatures.
Carnot efficiency	UK: /kɑːˈnəʊ ɪˈfɪʃənsi/ US: /kɑːrˈnoʊ ɪˈfɪʃənsi/	The maximum theoretical efficiency of a reversible heat engine operating between two specified reservoir temperatures.
Clausius sign convention	UK: /ˈklaʊziəs saɪn kənˈvenʃən/ US: /ˈklaʊziəs saɪn kənˈvenʃən/	The sign convention in which $Q$ is positive for resultant thermal energy supplied to a system and $W$ is positive for resultant work done by the system.
Clausius form	UK: /ˈklaʊziəs fɔːm/ US: /ˈklaʊziəs fɔːrm/	A form of the second law stating that no cyclic process can have as its sole effect the transfer of energy as heat from a colder body to a hotter body.
closed system	UK: /kləʊzd ˈsɪstəm/ US: /kloʊzd ˈsɪstəm/	A system that can exchange energy with its surroundings but does not exchange matter across its boundary.
compression	UK: /kəmˈpreʃən/ US: /kəmˈpreʃən/	A process in which the volume of a system decreases.
cyclic process	UK: /ˈsaɪklɪk ˈprəʊses/ US: /ˈsaɪklɪk ˈprɑːses/	A process that returns a system to its initial thermodynamic state.
entropy	UK: /ˈentrəpi/ US: /ˈentrəpi/	A thermodynamic quantity related to the degree of disorder of the particles in a system; $S=k_{\mathrm B}\ln\Omega$, where $\Omega$ is the number of possible microstates.
entropy change	UK: /ˈentrəpi tʃeɪndʒ/ US: /ˈentrəpi tʃeɪndʒ/	The difference between final and initial entropy; for a reversible transfer of thermal energy at absolute temperature $T$, $\Delta S=\Delta Q/T$.
expansion	UK: /ɪkˈspænʃən/ US: /ɪkˈspænʃən/	A process in which the volume of a system increases.
first law of thermodynamics	UK: /fɜːst lɔː əv ˌθɜːməʊdaɪˈnæmɪks/ US: /fɝːst lɔː əv ˌθɝːmoʊdaɪˈnæmɪks/	Using the IB sign convention, $Q=\Delta U+W$, where $W$ is the work done by the system.
heat	UK: /hiːt/ US: /hiːt/	Energy transferred between systems solely because of a temperature difference.
heat engine	UK: /hiːt ˈendʒɪn/ US: /hiːt ˈendʒən/	A cyclic device that absorbs energy by heating from a hot reservoir, does net work and rejects energy to a colder reservoir.
internal energy	UK: /ɪnˈtɜːnəl ˈenədʒi/ US: /ˌɪnˈtɝːnəl ˈenɚdʒi/	The sum of the random kinetic energies of the particles in a system and the potential energies associated with their interactions.
irreversible process	UK: /ɪrɪˈvɜːsəbəl ˈprəʊses/ US: /ˌɪrɪˈvɝːsəbəl ˈprɑːses/	A process that cannot be reversed while restoring both the system and surroundings to their initial states with no other net change.
isobaric process	UK: /ˌaɪsəʊˈbærɪk ˈprəʊses/ US: /ˌaɪsoʊˈbærɪk ˈprɑːses/	A thermodynamic process at constant pressure.
isochoric process	UK: /ˌaɪsəʊˈkɒrɪk ˈprəʊses/ US: /ˌaɪsoʊˈkɔːrɪk ˈprɑːses/	A thermodynamic process at constant volume.
isolated system	UK: /ˈaɪsəleɪtɪd ˈsɪstəm/ US: /ˈaɪsəleɪtɪd ˈsɪstəm/	A system across whose boundary neither matter nor energy is transferred.
isothermal process	UK: /ˌaɪsəʊˈθɜːməl ˈprəʊses/ US: /ˌaɪsoʊˈθɝːməl ˈprɑːses/	A thermodynamic process at constant temperature.
isovolumetric process	UK: /ˌaɪsəʊˌvɒljʊˈmetrɪk ˈprəʊses/ US: /ˌaɪsoʊˌvɑːljəˈmetrɪk ˈprɑːses/	A thermodynamic process at constant volume; also called an isochoric process.
Kelvin form	UK: /ˈkel.vɪn fɔːm/ US: /ˈkel.vɪn fɔːrm/	A form of the second law stating that no cyclic heat engine can convert all energy transferred from a single thermal reservoir into work.
microstate	UK: /ˈmaɪkrəʊsteɪt/ US: /ˈmaɪkroʊsteɪt/	One possible microscopic arrangement of the particles consistent with the macroscopic properties of a system.
pressure-volume diagram	UK: /ˈpreʃə ˈvɒljuːm ˈdaɪəɡræm/ US: /ˈpreʃɚ ˈvɑːljuːm ˈdaɪəɡræm/	A graph showing pressure as a function of volume during a thermodynamic process.
pressure-volume work	UK: /ˈpreʃə ˈvɒljuːm wɜːk/ US: /ˈpreʃɚ ˈvɑːljuːm wɝːk/	Work done by a system as its volume changes against an external pressure; for constant pressure $P$, $W=P\Delta V$.
reversible process	UK: /rɪˈvɜːsəbəl ˈprəʊses/ US: /rɪˈvɝːsəbəl ˈprɑːses/	An ideal process that can be reversed without net change to system and surroundings.
second law of thermodynamics	UK: /ˈsekənd lɔː əv ˌθɜːməʊdaɪˈnæmɪks/ US: /ˈsekənd lɔː əv ˌθɝːmoʊdaɪˈnæmɪks/	In an isolated system, total entropy cannot decrease; this determines the allowed direction of spontaneous macroscopic processes.
state variable	UK: /steɪt ˈveə.ri.ə.bəl/ US: /steɪt ˈver.i.ə.bəl/	A macroscopic quantity determined by the equilibrium state of a system.
surroundings	UK: /səˈraʊndɪŋz/ US: /sɚˈaʊndɪŋz/	Everything outside the chosen thermodynamic system.
thermal reservoir	UK: /ˈθɜːməl ˈrezəvˌwɑː/ US: /ˈθɝːməl ˈrezəvˌwɑːr/	A body that can exchange energy without appreciable temperature change.
thermodynamic system	UK: /ˌθɜːməʊdaɪˈnæmɪk ˈsɪstəm/ US: /ˌθɝːmoʊdaɪˈnæmɪk ˈsɪstəm/	The matter or region selected for thermodynamic analysis.
thermodynamics	UK: /ˌθɜːməʊdaɪˈnæmɪks/ US: /ˌθɝːmoʊdaɪˈnæmɪks/	The study of energy transfer, heat, work and macroscopic state changes.
work	UK: /wɜːk/ US: /wɝːk/	Energy transferred by a force when its point of application moves.

B.5 Current and circuits

SL and HL

Term	Pronunciation	Definition
ammeter	UK: /ˈæm.iː.tə/ US: /ˈæm.iː.t̬ɚ/	An instrument connected in series to measure current; an ideal ammeter has zero resistance.
anode	UK: /ˈænəʊd/ US: /ˈænoʊd/	The electrode at which oxidation occurs in an electrochemical cell; in other devices it is conventionally the electrode through which conventional current enters. Its polarity depends on the device.
battery	UK: /ˈbætəri/ US: /ˈbætɚi/	One or more cells connected to act as an electrical source.
cathode	UK: /ˈkæθəʊd/ US: /ˈkæθoʊd/	The electrode at which reduction occurs in an electrochemical cell; in other devices it is conventionally the electrode through which conventional current leaves. Its polarity depends on the device.
cell	UK: /sel/ US: /sel/	A source that transfers energy from a non-electrical form to electrical energy and maintains an electromotive force.
charge carrier	UK: /tʃɑːdʒ ˈkærɪə/ US: /tʃɑːrdʒ ˈkæriər/	A mobile particle that transports electric charge.
charge-carrier mobility	UK: /ˈtʃɑːdʒ ˌkæriə məʊˈbɪləti/ US: /ˈtʃɑːrdʒ ˌkæriər moʊˈbɪləti/	The drift velocity acquired by a charge carrier per unit electric field strength in a material.
chemical cell	UK: /ˈkemɪkəl sel/ US: /ˈkemɪkəl sel/	A cell that uses chemical reactions to transfer chemical energy to electrical energy and maintain an emf.
circuit diagram	UK: /ˈsɜːkɪt ˈdaɪəɡræm/ US: /ˈsɝːkət ˈdaɪəɡræm/	A representation of circuit connections using standardized component symbols.
conventional current	UK: /kənˈvenʃənəl ˈkʌrənt/ US: /kənˈvenʃənəl ˈkɝːənt/	The direction assigned to current as the direction in which positive charge would move.
current-voltage characteristic	UK: /ˈkʌrənt ˈvəʊltɪdʒ ˌkærɪktəˈrɪstɪk/ US: /ˈkɝːənt ˈvoʊltədʒ ˌkerəktɚˈɪstɪk/	A graph showing how current depends on potential difference for a component.
diode	UK: /ˈdaɪəʊd/ US: /ˈdaɪoʊd/	A non-ohmic semiconductor component that conducts much more readily in one direction than the other.
direct current	UK: /daɪˈrekt ˈkʌrənt/ US: /dəˈrekt ˈkɝːənt/	Electric current whose direction does not reverse with time.
earth (ground)	UK: /ɜːθ ɡraʊnd/ US: /ɝːθ ɡraʊnd/	A conducting connection assigned zero reference potential, often physically connected to Earth for safety or as a common circuit reference.
electric current	UK: /ɪˈlektrɪk ˈkʌrənt/ US: /ɪˈlektrɪk ˈkɝːənt/	The rate at which electric charge passes through a chosen cross-section.
electric heater	UK: /ɪˈlektrɪk ˈhiːtə/ US: /ɪˈlektrɪk ˈhiːtɚ/	A device that transfers electrical energy to internal energy through resistive heating.
electrical conductor	UK: /ɪˈlektrɪkəl kənˈdʌk.tə/ US: /ɪˈlektrɪkəl kənˈdʌk.tɚ/	A material in which mobile charge carriers can move readily in response to an electric field.
electrical insulator	UK: /ɪˈlektrɪkəl ˈɪnsjʊleɪtə/ US: /ɪˈlektrɪkəl ˈɪnsəleɪtɚ/	A material with very few mobile charge carriers, so it conducts little current under ordinary conditions.
electrical power	UK: /ɪˈlektrɪkəl ˈpaʊə/ US: /ɪˈlektrɪkəl ˈpaʊɚ/	The rate at which electrical energy is transferred.
electrode	UK: /ɪˈlektrəʊd/ US: /ɪˈlektroʊd/	A conductor through which charge enters or leaves an electrolyte, semiconductor, vacuum or other non-metallic medium.
electrolyte	UK: /ɪˈlektrəlaɪt/ US: /ɪˈlektrəlaɪt/	A substance containing mobile ions that conducts electric current by ionic motion.
electromotive force	UK: /ɪˌlektrəʊˈməʊtɪv fɔːs/ US: /ɪˌlektroʊˈmoʊtɪv fɔːrs/	The energy supplied by a source per unit charge passing through the source.
heating element	UK: /ˈhiːtɪŋ ˈelɪmənt/ US: /ˈhiːtɪŋ ˈeləmənt/	A resistive component designed to transfer electrical energy to internal energy by heating.
ideal ammeter	UK: /aɪˈdiː.əl ˈæm.iː.tə/ US: /aɪˈdiː.əl ˈæm.iː.t̬ɚ/	An ammeter modelled with zero resistance so that it does not change the current being measured.
ideal voltmeter	UK: /aɪˈdiː.əl ˈvəʊltˌmiːtə/ US: /aɪˈdiː.əl ˈvoʊltˌmiːtər/	A voltmeter modelled with infinite resistance so that it draws no current from the circuit being measured.
internal resistance	UK: /ɪnˈtɜːnəl rɪˈzɪstəns/ US: /ˌɪnˈtɝːnəl rɪˈzɪstəns/	The effective resistance inside a source of electromotive force.
junction	UK: /ˈdʒʌŋkʃən/ US: /ˈdʒʌŋkʃən/	A point in a circuit where current paths meet or divide.
lamp	UK: /læmp/ US: /læmp/	A circuit component that transfers electrical energy to light and internal energy when current flows.
light-dependent resistor	UK: /ˈlaɪt dɪˌpendənt rɪˈzɪstə/ US: /ˈlaɪt dɪˌpendənt rɪˈzɪstɚ/	A resistor whose resistance changes with incident light intensity, usually decreasing as intensity increases.
light-emitting diode	UK: /ˈlaɪt ɪˌmɪtɪŋ ˈdaɪəʊd/ US: /ˈlaɪt ɪˌmɪtɪŋ ˈdaɪoʊd/	A diode that emits light when forward biased and carrying current.
lost volts	UK: /lɒst vəʊlts/ US: /lɔːst voʊlts/	The potential difference across a source’s internal resistance when current flows.
motor	UK: /ˈməʊtə/ US: /ˈmoʊtɚ/	A device that transfers electrical energy to mechanical energy.
non-ohmic component	UK: /nɒn ˈəʊmɪk kəmˈpəʊnənt/ US: /nɑːn ˈoʊmɪk kəmˈpoʊnənt/	A component whose current is not proportional to potential difference.
Ohm’s law	UK: /əʊmz lɔː/ US: /oʊmz lɔː/	For an ohmic conductor under constant physical conditions, current is proportional to potential difference.
ohmic conductor	UK: /ˈəʊmɪk kənˈdʌk.tə/ US: /ˈoʊmɪk kənˈdʌk.tɚ/	A conductor that obeys Ohm’s law over the range considered.
open circuit	UK: /ˈəʊpən ˈsɜːkɪt/ US: /ˈoʊpən ˈsɝːkət/	A circuit with a break in its conducting path, so no steady current flows around the complete circuit.
parallel circuit	UK: /ˈpærəˌlel ˈsɜːkɪt/ US: /ˈperəˌlel ˈsɝːkət/	A circuit arrangement with branches connected across the same two junctions.
potential difference	UK: /pəˈtenʃəl ˈdɪf.ər.əns/ US: /pəˈtenʃəl ˈdɪf.ɚ.əns/	The energy transferred per unit charge between two points, $V=W/q$.
potential divider	UK: /pəˈtenʃəl dɪˈvaɪdə/ US: /pəˈtenʃəl dɪˈvaɪdɚ/	A series circuit used to provide a chosen fraction of an input potential difference.
potentiometer	UK: /pəˌtenʃiˈɒmɪtə/ US: /pəˌtenʃiˈɑːmətɚ/	A three-terminal variable resistor used as an adjustable potential divider.
resistance	UK: /rɪˈzɪstəns/ US: /rɪˈzɪstəns/	For a component at a stated operating condition, the ratio of potential difference across it to current through it.
resistivity	UK: /ˌriːzɪˈstɪvəti/ US: /ˌriːzɪˈstɪvəti/	A material property defined for a uniform conductor by $\rho=RA/L$.
resistor	UK: /rɪˈzɪstə/ US: /rɪˈzɪstɚ/	A circuit component designed to provide a specified electrical resistance.
rheostat	UK: /ˈriːəstæt/ US: /ˈriːoʊstæt/	A variable resistor used with two terminals to control current by changing the resistance in series with a circuit.
series circuit	UK: /ˈsɪəriːz ˈsɜːkɪt/ US: /ˈsɪriz ˈsɝːkət/	A circuit arrangement in which components carry the same current in one path.
short circuit	UK: /ʃɔːt ˈsɜːkɪt/ US: /ʃɔːrt ˈsɝːkət/	A very low-resistance path that can produce a large current.
solar cell	UK: /ˈsəʊlə sel/ US: /ˈsoʊlɚ sel/	A photovoltaic device that transfers energy from incident radiation to electrical energy.
switch	UK: /swɪtʃ/ US: /swɪtʃ/	A component used to open or close a conducting path in a circuit.
terminal	UK: /ˈtɜːmɪnəl/ US: /ˈtɝːmənəl/	A conducting point at which a component or source is connected to the rest of a circuit.
terminal potential difference	UK: /ˈtɜːmɪnəl pəˈtenʃəl ˈdɪf.ər.əns/ US: /ˈtɝːmənəl pəˈtenʃəl ˈdɪf.ɚ.əns/	The potential difference measured across the terminals of a source.
thermistor	UK: /θɜːˈmɪstə/ US: /θɝːˈmɪstɚ/	A resistor whose resistance changes strongly with temperature.
variable resistor	UK: /ˈveə.ri.ə.bəl rɪˈzɪstə/ US: /ˈver.i.ə.bəl rɪˈzɪstɚ/	A resistor whose resistance can be adjusted.
voltmeter	UK: /ˈvəʊltmiːtə/ US: /ˈvoʊltmiːtɚ/	An instrument connected in parallel to measure potential difference; an ideal voltmeter has infinite resistance.

C.1 Simple harmonic motion

SL and HL

Term	Pronunciation	Definition
amplitude	UK: /ˈæm.plɪ.tjuːd/ US: /ˈæm.plə.tuːd/	The maximum magnitude of an oscillating quantity relative to its equilibrium value.
angular frequency	UK: /ˈæŋ.ɡjə.lə ˈfriːkwənsi/ US: /ˈæŋ.ɡjə.lɚ ˈfriːkwənsi/	The phase change per unit time in radians.
antiphase	UK: /ˈæntɪfeɪz/ US: /ˈæntɪfeɪz/	Differing in phase by half a cycle or pi radians.
displacement	UK: /dɪˈspleɪs.mənt/ US: /dɪˈspleɪs.mənt/	The signed change in position from equilibrium along the axis of oscillation.
equilibrium position	UK: /ˌiːkwɪˈlɪbrɪəm pəˈzɪʃən/ US: /ˌiːkwəˈlɪbriəm pəˈzɪʃən/	The stable position about which the system oscillates and at which the resultant force is zero.
frequency	UK: /ˈfriːkwənsi/ US: /ˈfriːkwənsi/	The number of complete oscillations per unit time.
harmonic oscillator	UK: /hɑːˈmɒnɪk ˈɒsɪleɪtə/ US: /hɑːrˈmɑːnɪk ˈɑːsəleɪtɚ/	An oscillator whose restoring influence is proportional to displacement from equilibrium and directed oppositely; ideally it undergoes simple harmonic motion.
in phase	UK: /ɪn feɪz/ US: /ɪn feɪz/	Having the same phase at the same time.
mass-spring system	UK: /mæs sprɪŋ ˈsɪstəm/ US: /mæs sprɪŋ ˈsɪstəm/	An oscillator consisting of a mass attached to an elastic spring.
oscillation	UK: /ˌɒsɪˈleɪʃən/ US: /ˌɑːsəˈleɪʃən/	Repeated motion about an equilibrium position.
periodic motion	UK: /ˌpɪərɪˈɒdɪk ˈməʊʃən/ US: /ˌpɪriˈɑːdɪk ˈmoʊʃən/	Motion that repeats after equal time intervals.
phase	UK: /feɪz/ US: /feɪz/	A quantity that specifies the position within an oscillation cycle relative to a chosen reference.
restoring force	UK: /rɪˈstɔːrɪŋ fɔːs/ US: /rɪˈstɔːrɪŋ fɔːrs/	A force directed towards the equilibrium position.
simple harmonic motion	UK: /ˈsɪmpəl hɑːˈmɒnɪk ˈməʊʃən/ US: /ˈsɪmpəl hɑːrˈmɑːnɪk ˈmoʊʃən/	Oscillation in which acceleration is proportional to displacement from equilibrium and directed oppositely to it.
simple pendulum	UK: /ˈsɪmpəl ˈpendjʊləm/ US: /ˈsɪmpəl ˈpendʒələm/	An ideal point mass suspended by a light inextensible string; for small angular displacements its motion approximates simple harmonic motion.
time period	UK: /taɪm ˈpɪərɪəd/ US: /taɪm ˈpɪriəd/	The time taken for one complete oscillation.
total energy	UK: /ˈtəʊtəl ˈenədʒi/ US: /ˈtoʊtəl ˈenɚdʒi/	The constant sum of kinetic and potential energies in undamped SHM.

AHL

Term	Pronunciation	Definition
phase angle	UK: /feɪz ˈæŋɡəl/ US: /feɪz ˈæŋɡəl/	The angular measure specifying the position within a cycle relative to a chosen reference, expressed in radians.

C.2 Wave model

SL and HL

Term	Pronunciation	Definition
amplitude	UK: /ˈæm.plɪ.tjuːd/ US: /ˈæm.plə.tuːd/	The maximum magnitude of an oscillating quantity relative to its equilibrium value.
compression	UK: /kəmˈpreʃən/ US: /kəmˈpreʃən/	A region of increased pressure and density in a longitudinal wave.
electromagnetic spectrum	UK: /ɪˌlektrəʊməɡˈnetɪk ˈspektrəm/ US: /ˌɪˌlektroʊmæɡˈnetɪk ˈspektrəm/	The complete range of electromagnetic wavelengths and frequencies.
electromagnetic wave	UK: /ɪˌlektrəʊməɡˈnetɪk weɪv/ US: /ˌɪˌlektroʊmæɡˈnetɪk weɪv/	A transverse wave of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation.
energy transfer	UK: /ˈenədʒi ˈtrænsfɜː/ US: /ˈenɚdʒi ˈtrænsfɝː/	The movement of energy from one system or part of a system to another, for example by work, heating or radiation.
frequency	UK: /ˈfriːkwənsi/ US: /ˈfriːkwənsi/	The number of complete wave cycles passing a point per unit time.
gamma ray	UK: /ˈɡæmə reɪ/ US: /ˈɡæmə reɪ/	A high-energy photon emitted in a nuclear transition.
longitudinal wave	UK: /ˌlɒŋ.ɡɪˈtʃuː.dɪ.nəl weɪv/ US: /ˌlɑːn.dʒəˈtuː.dɪ.nəl weɪv/	A wave in which the relevant oscillation is parallel to the direction of propagation.
mechanical wave	UK: /mɪˈkænɪkəl weɪv/ US: /məˈkænɪkəl weɪv/	A wave that requires a material medium.
medium	UK: /ˈmiːdiəm/ US: /ˈmiːdiəm/	The material through which a mechanical wave propagates by local particle interactions.
microphone	UK: /ˈmaɪkrəfəʊn/ US: /ˈmaɪkrəfoʊn/	A transducer that converts sound waves into an electrical signal.
microwave	UK: /ˈmaɪkrəweɪv/ US: /ˈmaɪkroʊweɪv/	Electromagnetic radiation with wavelengths between infrared radiation and radio waves in the conventional spectrum classification.
oscilloscope	UK: /əˈsɪləskəʊp/ US: /əˈsɪləskoʊp/	An instrument that displays an electrical signal, commonly as potential difference against time.
particle displacement	UK: /ˈpɑːtɪkəl dɪˈspleɪs.mənt/ US: /ˈpɑːrtɪkəl dɪˈspleɪs.mənt/	The displacement of a particle of a medium from its equilibrium position as a wave passes.
period	UK: /ˈpɪərɪəd/ US: /ˈpɪriəd/	The time taken for one complete cycle.
phase difference	UK: /feɪz ˈdɪf.ər.əns/ US: /feɪz ˈdɪf.ɚ.əns/	The difference in phase between two oscillations or points on a wave.
radio wave	UK: /ˈreɪdiəʊ weɪv/ US: /ˈreɪdioʊ weɪv/	Electromagnetic radiation in the long-wavelength, low-frequency region of the electromagnetic spectrum.
rarefaction	UK: /ˌreə.rɪˈfæk.ʃən/ US: /ˌrer.əˈfæk.ʃən/	A region of decreased pressure and density in a longitudinal wave.
sound wave	UK: /saʊnd weɪv/ US: /saʊnd weɪv/	A mechanical wave that propagates through a material medium; in a fluid it consists of longitudinal pressure and density variations.
transverse wave	UK: /trænsˈvɜːs weɪv/ US: /trænzˈvɝːs weɪv/	A wave in which the relevant oscillation is perpendicular to the direction of propagation.
travelling wave	UK: /ˈtrævlɪŋ weɪv/ US: /ˈtrævəlɪŋ weɪv/	A wave pattern that propagates through space or a medium.
ultraviolet radiation	UK: /ˌʌltrəˈvaɪələt ˌreɪdɪˈeɪʃən/ US: /ˌʌltrəˈvaɪələt ˌreɪdiˈeɪʃən/	Electromagnetic radiation with wavelengths shorter than visible light and longer than X-rays.
vacuum	UK: /ˈvækjuəm/ US: /ˈvækjuəm/	A region containing no matter in the ideal model; electromagnetic waves can propagate through it, whereas mechanical waves cannot.
visible light	UK: /ˈvɪzəbəl laɪt/ US: /ˈvɪzəbəl laɪt/	The part of the electromagnetic spectrum detectable by the human eye, approximately 400–700 nm.
wave	UK: /weɪv/ US: /weɪv/	A disturbance that propagates and transfers energy without a resultant transfer of matter.
wave speed	UK: /weɪv spiːd/ US: /weɪv spiːd/	The speed at which a specified phase of a wave propagates.
wavelength	UK: /ˈweɪv.leŋθ/ US: /ˈweɪv.leŋθ/	The shortest distance, measured along the direction of propagation, between two points in the same phase.
X-ray	UK: /ˈeks reɪ/ US: /ˈeks reɪ/	High-frequency ionizing electromagnetic radiation commonly produced when high-speed electrons are decelerated or change energy states; X-ray and gamma-ray energy ranges overlap.

C.3 Wave phenomena

SL and HL

Term	Pronunciation	Definition
angle of incidence	UK: /ˈæŋɡəl əv ˈɪnsɪdəns/ US: /ˈæŋɡəl əv ˈɪnsədəns/	The angle between an incident ray and the normal.
angle of refraction	UK: /ˈæŋɡəl əv rɪˈfrækʃən/ US: /ˈæŋɡəl əv rɪˈfrækʃən/	The angle between a refracted ray and the normal.
aperture	UK: /ˈæpətʃə/ US: /ˈæpɚtʃɚ/	An opening through which a wave passes.
boundary	UK: /ˈbaʊndri/ US: /ˈbaʊndɚi/	The interface between two media or regions.
coherent sources	UK: /kəʊˈhɪərənt ˈsɔːsɪz/ US: /koʊˈhɪrənt ˈsɔːrsəz/	Sources that produce waves of the same frequency with a constant phase difference.
constructive interference	UK: /kənˈstrʌktɪv ˌɪntəˈfɪərəns/ US: /kənˈstrʌktɪv ˌɪntɚˈfɪrəns/	Interference that produces increased resultant amplitude.
critical angle	UK: /ˈkrɪtɪkəl ˈæŋɡəl/ US: /ˈkrɪtɪkəl ˈæŋɡəl/	For a wave travelling from higher to lower refractive index, the angle of incidence that gives a refracted angle of $90^\circ$.
destructive interference	UK: /dɪˈstrʌktɪv ˌɪntəˈfɪərəns/ US: /dɪˈstrʌktɪv ˌɪntɚˈfɪrəns/	Interference that produces reduced or zero resultant amplitude.
diffraction	UK: /dɪˈfrækʃən/ US: /dɪˈfrækʃən/	The spreading of a wave as it passes through an aperture or past an obstacle, most evident when the relevant dimension is comparable with the wavelength.
double-slit interference	UK: /ˈdʌbəl slɪt ˌɪntəˈfɪərəns/ US: /ˈdʌbəl slɪt ˌɪntɚˈfɪrəns/	An interference pattern produced by two narrow coherent openings.
double-source interference	UK: /ˈdʌbəl sɔːs ˌɪntəˈfɪərəns/ US: /ˈdʌbəl sɔːrs ˌɪntɚˈfɪrəns/	Interference produced by waves from two coherent sources.
fringe spacing	UK: /frɪndʒ ˈspeɪsɪŋ/ US: /frɪndʒ ˈspeɪsɪŋ/	The distance between adjacent bright or dark interference fringes.
incident wave	UK: /ˈɪn.sɪ.dənt weɪv/ US: /ˈɪn.sɪ.dənt weɪv/	A wave travelling towards a boundary or obstacle.
interference	UK: /ˌɪntəˈfɪərəns/ US: /ˌɪntɚˈfɪrəns/	The variation of resultant amplitude or intensity when waves overlap according to the principle of superposition; a stable pattern requires coherent sources.
normal incidence	UK: /ˈnɔːməl ˈɪnsɪdəns/ US: /ˈnɔːrməl ˈɪnsədəns/	Incidence in which the incoming ray or wave direction is perpendicular to the boundary or aperture plane.
path difference	UK: /pɑːθ ˈdɪf.ər.əns/ US: /pæθ ˈdɪf.ɚ.əns/	The difference in distances travelled by two waves to a point.
ray	UK: /reɪ/ US: /reɪ/	A geometrical line normal to wavefronts that indicates the local direction of wave propagation and energy transfer.
reflected wave	UK: /rɪˈflektɪd weɪv/ US: /rɪˈflektɪd weɪv/	A wave that returns into the original medium after meeting a boundary.
reflection	UK: /rɪˈflekʃən/ US: /rɪˈflekʃən/	The return of a wave into its original medium at a boundary.
refraction	UK: /rɪˈfrækʃən/ US: /rɪˈfrækʃən/	A change in wave speed on entering another medium, generally accompanied by a change in direction except at normal incidence.
refractive index	UK: /rɪˈfræktɪv ˈɪndeks/ US: /rəˈfræktɪv ˈɪndeks/	For light in a medium, the ratio of its speed in vacuum to its phase speed in the medium.
ripple tank	UK: /ˈrɪpəl tæŋk/ US: /ˈrɪpəl tæŋk/	A shallow water tank used to generate and observe two-dimensional surface-wave patterns.
screen	UK: /skriːn/ US: /skriːn/	A surface on which an interference or diffraction pattern is observed or recorded.
slit	UK: /slɪt/ US: /slɪt/	A narrow aperture through which waves pass in diffraction or interference experiments.
slit separation	UK: /slɪt ˌsepəˈreɪʃən/ US: /slɪt ˌsepəˈreɪʃən/	The centre-to-centre distance between adjacent slits in an interference arrangement.
Snell’s law	UK: /snelz lɔː/ US: /snelz lɔː/	The relation between angles of incidence and refraction and refractive indices.
superposition	UK: /ˌsuːpəpəˈzɪʃən/ US: /ˌsuːpərpəˈzɪʃən/	The principle that the resultant displacement or field at a point is the algebraic or vector sum of the individual contributions.
total internal reflection	UK: /ˈtəʊtəl ɪnˈtɜːnəl rɪˈflekʃən/ US: /ˈtoʊtəl ˌɪnˈtɝːnəl rɪˈflekʃən/	Complete reflection at a boundary when a wave travels from higher to lower refractive index and the incident angle exceeds the critical angle.
transmission	UK: /ˌtrænˈsmɪʃən/ US: /trænˈsmɪʃən/	The passage of a wave, or part of it, and associated energy through a boundary into another region or medium.
transmitted wave	UK: /trænzˈmɪtɪd weɪv/ US: /trænzˈmɪtɪd weɪv/	A wave that passes through a boundary into the second medium.
wave generator	UK: /weɪv ˈdʒen.ər.eɪ.tə/ US: /weɪv ˈdʒen.ər.eɪ.t̬ɚ/	A device that produces periodic disturbances in a medium for the study of waves.
wave pulse	UK: /weɪv pʌls/ US: /weɪv pʌls/	A single localized disturbance that propagates through a medium or field.
wavefront	UK: /ˈweɪvfrʌnt/ US: /ˈweɪvfrʌnt/	A line or surface joining points of equal phase.
Young’s double-slit experiment	UK: /jʌŋz ˈdʌbəl slɪt ɪkˈsperɪmənt/ US: /jʌŋz ˈdʌbəl slɪt ɪkˈsperəmənt/	An experiment in which coherent light from two slits forms an interference pattern, demonstrating the wave behaviour of light.

AHL

Term	Pronunciation	Definition
central maximum	UK: /ˈsentrəl ˈmæksɪməm/ US: /ˈsentrəl ˈmæksəməm/	The central bright region of a diffraction intensity pattern, lying between the first minima on either side.
diffraction grating	UK: /dɪˈfrækʃən ˈɡreɪtɪŋ/ US: /dɪˈfrækʃən ˈɡreɪtɪŋ/	An optical element containing many equally spaced parallel slits.
intensity pattern	UK: /ɪnˈtensɪti ˈpætən/ US: /ɪnˈtensəti ˈpætɚn/	The spatial variation of wave intensity produced by interference or diffraction.
monochromatic light	UK: /ˌmɒnəkrəˈmætɪk laɪt/ US: /ˌmɑːnəkroʊˈmætɪk laɪt/	Light with a single frequency, or a very narrow range of frequencies.
multiple-slit interference	UK: /ˈmʌltɪpəl slɪt ˌɪntəˈfɪərəns/ US: /ˈmʌltəpəl slɪt ˌɪntɚˈfɪrəns/	Interference produced by coherent waves emerging from more than two slits.
order	UK: /ˈɔːdə/ US: /ˈɔːrdɚ/	An integer label identifying an interference maximum.
rectangular slit	UK: /rekˈtæŋ.ɡjə.lə slɪt/ US: /rekˈtæŋ.ɡjə.lɚ slɪt/	A narrow rectangular aperture used to produce a single-slit diffraction pattern.
single-slit diffraction	UK: /ˈsɪŋɡəl slɪt dɪˈfrækʃən/ US: /ˈsɪŋɡəl slɪt dɪˈfrækʃən/	The spreading and interference pattern produced when a wave passes through one narrow slit.
slit width	UK: /slɪt wɪdθ/ US: /slɪt wɪdθ/	The transverse width of an individual slit, which controls the angular spread of its diffraction pattern.
white light	UK: /waɪt laɪt/ US: /waɪt laɪt/	Visible light containing a broad range of wavelengths, which can produce separated colours in a diffraction pattern.

C.4 Standing waves and resonance

SL and HL

Term	Pronunciation	Definition
antinode	UK: /ˈæn.ti.nəʊd/ US: /ˈæn.t̬i.noʊd/	A point in a standing wave at which the relevant oscillating quantity has maximum amplitude.
boundary condition	UK: /ˈbaʊndri kənˈdɪʃən/ US: /ˈbaʊndɚi kənˈdɪʃən/	A physical constraint imposed at the boundary of a wave system.
closed pipe	UK: /kləʊzd paɪp/ US: /kloʊzd paɪp/	An air column with a closed end that acts as a displacement node.
critical damping	UK: /ˈkrɪtɪkəl ˈdæmpɪŋ/ US: /ˈkrɪtɪkəl ˈdæmpɪŋ/	The minimum damping that returns a displaced system to equilibrium without oscillation.
damping	UK: /ˈdæmpɪŋ/ US: /ˈdæmpɪŋ/	A process that removes mechanical energy from an oscillator and reduces its amplitude.
displacement antinode	UK: /dɪˈspleɪs.mənt ˈæn.ti.nəʊd/ US: /dɪˈspleɪs.mənt ˈæn.t̬i.noʊd/	A point in a standing wave at which the displacement amplitude is maximum.
displacement node	UK: /dɪˈspleɪs.mənt nəʊd/ US: /dɪˈspleɪs.mənt noʊd/	A point in a standing wave at which the displacement is always zero.
driven oscillator	UK: /ˈdrɪvən ˈɒsɪleɪtə/ US: /ˈdrɪvən ˈɑːsəleɪtɚ/	An oscillator acted on by an external periodic driving force.
driving frequency	UK: /ˈdraɪvɪŋ ˈfriːkwənsi/ US: /ˈdraɪvɪŋ ˈfriːkwənsi/	The frequency of an external periodic force.
first harmonic	UK: /fɜːst hɑːˈmɒnɪk/ US: /fɝːst hɑːrˈmɑːnɪk/	The lowest-frequency standing-wave mode allowed by the boundary conditions.
fixed end	UK: /fɪkst end/ US: /fɪkst end/	A boundary at which displacement must be zero.
free end	UK: /friː end/ US: /friː end/	A boundary at which displacement can be maximum.
frequency response	UK: /ˈfriːkwənsi rɪˈspɒns/ US: /ˈfriːkwənsi rɪˈspɑːns/	The variation of steady-state oscillation amplitude with driving frequency.
harmonic	UK: /hɑːˈmɒnɪk/ US: /hɑːrˈmɑːnɪk/	An allowed standing-wave mode; when the modes form an integer harmonic series, its frequency is an integer multiple of the first-harmonic frequency.
heavy damping	UK: /ˈhevi ˈdæmpɪŋ/ US: /ˈhevi ˈdæmpɪŋ/	Damping strong enough that oscillations are suppressed and the system returns slowly towards equilibrium.
light damping	UK: /laɪt ˈdæmpɪŋ/ US: /laɪt ˈdæmpɪŋ/	Weak damping that allows oscillations of gradually decreasing amplitude.
mode	UK: /məʊd/ US: /moʊd/	A permitted pattern of oscillation determined by boundary conditions.
natural frequency	UK: /ˈnætʃ.ər.əl ˈfriːkwənsi/ US: /ˈnætʃ.ɚ.əl ˈfriːkwənsi/	A frequency at which a system oscillates freely.
node	UK: /nəʊd/ US: /noʊd/	A point in a standing wave at which the relevant oscillating quantity has zero amplitude.
nth harmonic	UK: /enθ hɑːˈmɒnɪk/ US: /enθ hɑːrˈmɑːnɪk/	A standing-wave mode whose frequency is $n$ times the first-harmonic frequency when the allowed modes form an integer harmonic series.
open pipe	UK: /ˈəʊpən paɪp/ US: /ˈoʊpən paɪp/	An air column with an open end that acts as a displacement antinode.
overdamping	UK: /ˌəʊvəˈdæmpɪŋ/ US: /ˌoʊvərˈdæmpɪŋ/	Damping stronger than critical, producing a slow non-oscillatory return.
relative amplitude	UK: /ˈrelətɪv ˈæm.plɪ.tjuːd/ US: /ˈrelətɪv ˈæm.plə.tuːd/	The amplitude at one point compared with that at another point in the same standing-wave pattern.
resonance	UK: /ˈrezənəns/ US: /ˈrezənəns/	A large steady-state response when a system is driven at or near one of its natural frequencies.
resonant frequency	UK: /ˈrezənənt ˈfriːkwənsi/ US: /ˈrezənənt ˈfriːkwənsi/	A driving frequency at which the steady-state amplitude of a driven oscillator is maximum for the stated damping.
signal generator	UK: /ˈsɪɡnəl ˈdʒen.ər.eɪ.tə/ US: /ˈsɪɡnəl ˈdʒen.ər.eɪ.t̬ɚ/	An instrument that supplies an electrical signal with adjustable waveform, frequency and amplitude.
standing wave	UK: /ˈstændɪŋ weɪv/ US: /ˈstændɪŋ weɪv/	A stationary oscillation pattern formed by superposition of waves of the same frequency and amplitude travelling in opposite directions.
string	UK: /strɪŋ/ US: /strɪŋ/	A flexible stretched medium that can support transverse travelling and standing waves.

C.5 Doppler effect

SL and HL

Term	Pronunciation	Definition
approaching source	UK: /əˈprəʊtʃɪŋ sɔːs/ US: /əˈproʊtʃɪŋ sɔːrs/	A wave source whose distance from the observer is decreasing.
blueshift	UK: /ˈbluːʃɪft/ US: /ˈbluːʃɪft/	A shift of spectral features towards shorter wavelengths and higher frequencies.
Doppler effect	UK: /ˈdɒp.lə ɪˈfekt/ US: /ˈdɑː.plɚ ɪˈfekt/	The change in observed frequency caused by relative radial motion between source and observer.
Doppler shift	UK: /ˈdɒp.lə ʃɪft/ US: /ˈdɑː.plɚ ʃɪft/	The change in observed frequency or wavelength caused by relative motion along the line of sight between source and observer.
fractional frequency shift	UK: /ˈfrækʃənəl ˈfriːkwənsi ʃɪft/ US: /ˈfrækʃənəl ˈfriːkwənsi ʃɪft/	The frequency change divided by the original frequency.
fractional wavelength shift	UK: /ˈfrækʃənəl ˈweɪv.leŋθ ʃɪft/ US: /ˈfrækʃənəl ˈweɪv.leŋθ ʃɪft/	The wavelength change divided by the original wavelength.
line of sight	UK: /laɪn əv saɪt/ US: /laɪn əv saɪt/	The straight direction from observer to source.
loudspeaker	UK: /ˌlaʊdˈspiːkə/ US: /ˌlaʊdˈspiːkɚ/	A transducer that converts an electrical signal into sound waves.
medical Doppler effect	UK: /ˈmedɪkəl ˈdɒp.lə ɪˈfekt/ US: /ˈmedɪkəl ˈdɑː.plɚ ɪˈfekt/	The use of Doppler frequency shifts, commonly with ultrasound, to determine motion such as blood-flow speed.
observed frequency	UK: /əbˈzɜːvd ˈfriːkwənsi/ US: /əbˈzɝːvd ˈfriːkwənsi/	The frequency measured by an observer.
radar	UK: /ˈreɪdɑː/ US: /ˈreɪdɑːr/	A system that transmits radio or microwave signals and analyses their reflections to determine properties such as range or radial speed.
radial velocity	UK: /ˈreɪ.di.əl vəˈlɒsɪti/ US: /ˈreɪ.di.əl vəˈlɑːsəti/	The component of velocity along the line of sight.
receding source	UK: /rɪˈsiːdɪŋ sɔːs/ US: /rɪˈsiːdɪŋ sɔːrs/	A wave source whose distance from the observer is increasing.
redshift	UK: /ˈredʃɪft/ US: /ˈredʃɪft/	A shift of spectral features towards longer wavelengths and lower frequencies.
relative speed	UK: /ˈrelətɪv spiːd/ US: /ˈrelətɪv spiːd/	The magnitude of the velocity of one object measured in the reference frame of another.
sound detector	UK: /saʊnd dɪˈtektə/ US: /saʊnd dɪˈtektɚ/	A device that converts incident sound into a measurable signal.
source frequency	UK: /sɔːs ˈfriːkwənsi/ US: /sɔːrs ˈfriːkwənsi/	The frequency emitted by the source in its rest frame.
spectral line	UK: /ˈspektrəl laɪn/ US: /ˈspektrəl laɪn/	A narrow wavelength feature produced by emission or absorption.

AHL

Term	Pronunciation	Definition
moving observer	UK: /ˈmuːvɪŋ əbˈzɜːvə/ US: /ˈmuːvɪŋ əbˈzɝːvɚ/	In a classical Doppler calculation, an observer with non-zero velocity relative to the medium.
moving source	UK: /ˈmuːvɪŋ sɔːs/ US: /ˈmuːvɪŋ sɔːrs/	In a classical Doppler calculation, a source with non-zero velocity relative to the medium.

D.1 Gravitational fields

SL and HL

Term	Pronunciation	Definition
aphelion	UK: /əˈfiːliən/ US: /əˈfiːliən/	The apoapsis of an orbit around the Sun.
apoapsis	UK: /ˌæpəʊˈæpsɪs/ US: /ˌæpoʊˈæpsɪs/	The point in an orbit farthest from the centre of the body being orbited.
apogee	UK: /ˈæpədʒiː/ US: /ˈæpədʒiː/	The apoapsis of an orbit around Earth.
apparent weightlessness	UK: /əˈpærənt ˈweɪtləsnəs/ US: /əˈperənt ˈweɪtləsnəs/	The condition in which the contact force supporting a body is zero, even though gravity may still act.
apsis	UK: /ˈæpsɪs/ US: /ˈæpsɪs/	A point in an orbit at which the orbiting body is nearest to or farthest from the centre of the body being orbited; the plural is apsides.
circular orbit	UK: /ˈsɜːkjʊlə ˈɔːbɪt/ US: /ˈsɝːkjələr ˈɔːrbət/	An orbit of constant radius.
Earth	UK: /ɜːθ/ US: /ɝːθ/	The third planet from the Sun.
eccentricity	UK: /ˌeksenˈtrɪsɪti/ US: /ˌeksenˈtrɪsəti/	A dimensionless parameter that determines the shape of a Keplerian orbit; for a bound ellipse, 0 ≤ e < 1, with e = 0 for a circle.
field line	UK: /fiːld laɪn/ US: /fiːld laɪn/	An imaginary curve whose tangent at each point gives the local direction of the field.
geostationary orbit	UK: /ˌdʒiːəʊˈsteɪʃənəri ˈɔːbɪt/ US: /ˌdʒiːoʊˈsteɪʃəneri ˈɔːrbət/	A circular equatorial orbit whose period equals Earth’s rotation period and direction is prograde.
gravitational constant	UK: /ˌɡrævɪˈteɪʃənəl ˈkɒnstənt/ US: /ˌɡrævɪˈteɪʃənəl ˈkɑːnstənt/	The universal proportionality constant in Newton’s law of gravitation.
gravitational field	UK: /ˌɡrævɪˈteɪʃənəl fiːld/ US: /ˌɡrævɪˈteɪʃənəl fiːld/	A region in which a mass experiences gravitational force.
gravitational field strength	UK: /ˌɡrævɪˈteɪʃənəl fiːld streŋθ/ US: /ˌɡrævɪˈteɪʃənəl fiːld streŋθ/	The gravitational force per unit mass on a small test mass; it is a vector.
Jupiter	UK: /ˈdʒuːpɪtə/ US: /ˈdʒuːpətɚ/	The fifth planet from the Sun and the largest planet in the Solar System.
Kepler’s laws	UK: /ˈkepləz lɔːz/ US: /ˈkeplərz lɔːz/	Three empirical laws describing planetary orbits.
Mars	UK: /mɑːz/ US: /mɑːrz/	The fourth planet from the Sun.
Mercury	UK: /ˈmɜːkjəri/ US: /ˈmɝːkjəri/	The first planet from the Sun and the smallest planet in the Solar System.
Moon	UK: /muːn/ US: /muːn/	Earth’s only natural satellite.
Neptune	UK: /ˈneptjuːn/ US: /ˈneptuːn/	The eighth and most distant planet from the Sun.
orbital motion	UK: /ˈɔːbɪtəl ˈməʊʃən/ US: /ˈɔːrbətəl ˈmoʊʃən/	Motion of one body around another under gravity.
orbital period	UK: /ˈɔːbɪtəl ˈpɪərɪəd/ US: /ˈɔːrbətəl ˈpɪriəd/	The time taken to complete one orbit.
periapsis	UK: /ˌperiˈæpsɪs/ US: /ˌperiˈæpsɪs/	The point in an orbit nearest to the centre of the body being orbited.
perigee	UK: /ˈperɪdʒiː/ US: /ˈperɪdʒiː/	The periapsis of an orbit around Earth.
perihelion	UK: /ˌperɪˈhiːliən/ US: /ˌperɪˈhiːliən/	The periapsis of an orbit around the Sun.
planet	UK: /ˈplænɪt/ US: /ˈplænət/	In the Solar System, a celestial body that orbits the Sun, is nearly spherical under its own gravity, and is gravitationally dominant in its orbital neighbourhood.
point mass	UK: /pɔɪnt mæs/ US: /pɔɪnt mæs/	An idealized body whose dimensions are negligible compared with the distances relevant to the problem.
radial field	UK: /ˈreɪ.di.əl fiːld/ US: /ˈreɪ.di.əl fiːld/	A field whose vectors point directly towards or away from one centre.
satellite	UK: /ˈsætəˌlaɪt/ US: /ˈsætəˌlaɪt/	A body that orbits another body.
Saturn	UK: /ˈsætən/ US: /ˈsætɚn/	The sixth planet from the Sun.
Solar System	UK: /ˈsəʊlə ˌsɪstəm/ US: /ˈsoʊlɚ ˌsɪstəm/	The Sun and all objects gravitationally bound to it.
spherical mass	UK: /ˈsferɪkəl mæs/ US: /ˈsferɪkəl mæs/	A spherically symmetric mass distribution treated externally as a point mass.
Sun	UK: /sʌn/ US: /sʌn/	The star at the centre of the Solar System, containing nearly all of the system’s mass.
superposition	UK: /ˌsuːpəpəˈzɪʃən/ US: /ˌsuːpərpəˈzɪʃən/	The principle that the resultant gravitational field is the vector sum of the fields produced independently by each mass.
two-body system	UK: /ˌtuː ˈbɒdi ˈsɪstəm/ US: /ˌtuː ˈbɑːdi ˈsɪstəm/	A system modelled as two interacting bodies, with their separation measured between their centres of mass when appropriate.
uniform gravitational field	UK: /ˈjuːnɪˌfɔːm ˌɡrævɪˈteɪʃənəl fiːld/ US: /ˈjuːnəˌfɔːrm ˌɡrævɪˈteɪʃənəl fiːld/	A gravitational field with constant magnitude and direction.
universal law of gravitation	UK: /ˌjuːnɪˈvɜːsəl lɔː əv ˌɡrævɪˈteɪʃən/ US: /ˌjuːnəˈvɝːsəl lɔː əv ˌɡrævɪˈteɪʃən/	Newton’s inverse-square law for the gravitational force between two point masses.
Uranus	UK: /ˈjʊərənəs/ US: /ˈjʊrənəs/	The seventh planet from the Sun.
Venus	UK: /ˈviːnəs/ US: /ˈviːnəs/	The second planet from the Sun.

AHL

Term	Pronunciation	Definition
atmospheric drag	UK: /ˌætməsˈferɪk dræɡ/ US: /ˌætməsˈferɪk dræɡ/	A resistive force exerted by an atmosphere on an orbiting body, transferring orbital mechanical energy to internal energy of the body and atmosphere.
binding energy	UK: /ˈbaɪndɪŋ ˈenədʒi/ US: /ˈbaɪndɪŋ ˈenɚdʒi/	The positive energy required to separate a bound system into specified free constituents.
equipotential surface	UK: /ˌiːkwɪpəˈtenʃəl ˈsɜːfɪs/ US: /ˌiːkwɪpəˈtenʃəl ˈsɝːfəs/	A surface on which gravitational potential is constant.
escape speed	UK: /ɪˈskeɪp spiːd/ US: /ɪˈskeɪp spiːd/	The minimum initial speed required to reach infinity with zero final speed when only the stated inverse-square gravitational field acts.
gravitational potential	UK: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl/ US: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl/	The gravitational potential energy per unit mass of a small test mass at a point, with potential defined as zero at infinity.
gravitational potential energy	UK: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl ˈenədʒi/ US: /ˌɡrævɪˈteɪʃənəl pəˈtenʃəl ˈenɚdʒi/	The energy of a system due to the relative positions of its masses; for two point masses with zero at infinity, $E_{\mathrm p}=-Gm_1m_2/r$.
orbital decay	UK: /ˈɔːbɪtəl dɪˈkeɪ/ US: /ˈɔːrbətəl dɪˈkeɪ/	A gradual reduction in orbital size caused by loss of orbital mechanical energy, for example through atmospheric drag.
orbital energy	UK: /ˈɔːbɪtəl ˈenədʒi/ US: /ˈɔːrbətəl ˈenɚdʒi/	The total mechanical energy of an orbiting two-body system, equal to the sum of its kinetic and gravitational potential energies.
orbital speed	UK: /ˈɔːbɪtəl spiːd/ US: /ˈɔːrbətəl spiːd/	The tangential speed of a body in orbit.
potential gradient	UK: /pəˈtenʃəl ˈɡreɪ.di.ənt/ US: /pəˈtenʃəl ˈɡreɪ.di.ənt/	The rate of change of potential with distance; for a radial gravitational field, $g=-\Delta V_{\mathrm g}/\Delta r$.

D.2 Electric and magnetic fields

SL and HL

Term	Pronunciation	Definition
air-core solenoid	UK: /ˈeə kɔː ˈsəʊlənɔɪd/ US: /ˈer kɔːr ˈsoʊlənɔɪd/	A solenoid with no ferromagnetic core, whose magnetic field is produced by current in its windings.
bar magnet	UK: /bɑː ˈmæɡnɪt/ US: /bɑːr ˈmæɡnət/	A permanent magnet with distinguishable north and south poles.
charging by contact	UK: /ˈtʃɑːdʒɪŋ baɪ ˈkɒn.tækt/ US: /ˈtʃɑːrdʒɪŋ baɪ ˈkɑːn.tækt/	Transfer and redistribution of charge when conductors touch.
charging by friction	UK: /ˈtʃɑːdʒɪŋ baɪ ˈfrɪkʃən/ US: /ˈtʃɑːrdʒɪŋ baɪ ˈfrɪkʃən/	Transfer of electrons when different materials are rubbed together.
circular coil	UK: /ˈsɜːkjʊlə kɔɪl/ US: /ˈsɝːkjələr kɔɪl/	A current-carrying conductor formed into a circular loop.
compass	UK: /ˈkʌmpəs/ US: /ˈkʌmpəs/	An instrument containing a magnetized needle that aligns with the local magnetic field direction.
conductor	UK: /kənˈdʌk.tə/ US: /kənˈdʌk.tɚ/	A material containing mobile charge carriers.
conservation of charge	UK: /ˌkɒnsəˈveɪʃən əv tʃɑːdʒ/ US: /ˌkɑːnsɚˈveɪʃən əv tʃɑːrdʒ/	The total electric charge of an isolated system remains constant.
Coulomb constant	UK: /ˈkuːlɒm ˌkɒnstənt/ US: /ˈkuːlɑːm ˌkɑːnstənt/	The proportionality constant in Coulomb’s law in vacuum, $k=\frac{1}{4\pi\varepsilon_0}$.
Coulomb’s law	UK: /ˈkuːlɒmz lɔː/ US: /ˈkuːlɑːmz lɔː/	The inverse-square relation for the magnitude and line of action of the electrostatic force between point charges.
current-carrying wire	UK: /ˈkʌrənt ˈkæriɪŋ ˈwaɪə/ US: /ˈkɝːənt ˈkæriɪŋ ˈwaɪɚ/	A wire through which electric current flows.
earthing	UK: /ˈɜːθɪŋ/ US: /ˈɝːθɪŋ/	Connecting a conductor to Earth so charge can flow to or from the large conducting reservoir of Earth.
edge effect	UK: /edʒ ɪˈfekt/ US: /edʒ ɪˈfekt/	The curvature and non-uniformity of field lines near the edges of finite plates.
electric charge	UK: /ɪˈlektrɪk tʃɑːdʒ/ US: /ɪˈlektrɪk tʃɑːrdʒ/	A conserved scalar property of matter that determines electric interactions; it may be positive or negative and is measured in coulombs.
electric field	UK: /ɪˈlektrɪk fiːld/ US: /ɪˈlektrɪk fiːld/	A vector field defined by the electric force per unit positive test charge.
electric field line	UK: /ɪˈlektrɪk fiːld laɪn/ US: /ɪˈlektrɪk fiːld laɪn/	An imaginary curve whose tangent gives the electric-field direction, conventionally the force direction on a positive test charge.
electric field strength	UK: /ɪˈlektrɪk fiːld streŋθ/ US: /ɪˈlektrɪk fiːld streŋθ/	The electric force per unit positive test charge at a point.
electroscope	UK: /ɪˈlektrəskəʊp/ US: /ɪˈlektroʊskoʊp/	An instrument used to detect electric charge through the force between charged parts.
electrostatic equilibrium	UK: /ɪˌlektrəʊˈstætɪk ˌiːkwɪˈlɪbrɪəm/ US: /ˌɪˌlektroʊˈstætɪk ˌiːkwəˈlɪbriəm/	A state in which charge in a conductor has no macroscopic motion and the electric field inside the conducting material is zero.
electrostatic induction	UK: /ɪˌlektrəʊˈstætɪk ɪnˈdʌk.ʃən/ US: /ˌɪˌlektroʊˈstætɪk ɪnˈdʌk.ʃən/	The redistribution of charge in a conductor caused by an external electric field, without direct contact with the inducing body.
elementary charge	UK: /ˌelɪˈmentəri tʃɑːdʒ/ US: /ˌeləˈmentri tʃɑːrdʒ/	The positive constant e equal to the magnitude of the charge of a proton or electron.
field-line density	UK: /fiːld laɪn ˈdensɪti/ US: /fiːld laɪn ˈdensəti/	A qualitative graphical indication of relative field magnitude; it is not itself a physical quantity.
grounding	UK: /ˈɡraʊndɪŋ/ US: /ˈɡraʊndɪŋ/	Connecting a conductor to Earth so charge can flow to or from it.
hollow charged conducting sphere	UK: /ˈhɒləʊ tʃɑːdʒd kənˈdʌktɪŋ sfɪə/ US: /ˈhɑːloʊ tʃɑːrdʒd kənˈdʌktɪŋ sfɪr/	An isolated charged spherical conducting shell; if its cavity contains no charge, the electric field is zero throughout the cavity and conductor, the potential is constant there, and the external field is that of a point charge at its centre.
iron filings	UK: /ˈaɪən ˈfaɪlɪŋz/ US: /ˈaɪɚn ˈfaɪlɪŋz/	Small iron particles that align in a magnetic field and reveal the field pattern qualitatively.
magnetic field	UK: /mæɡˈnetɪk fiːld/ US: /mæɡˈnetɪk fiːld/	A vector field that exerts forces on moving charges, electric currents and magnetic dipoles.
magnetic field line	UK: /mæɡˈnetɪk fiːld laɪn/ US: /mæɡˈnetɪk fiːld laɪn/	A closed curve whose tangent gives the local direction of the magnetic field.
Millikan’s oil-drop experiment	UK: /ˈmɪlɪkənz ˈɔɪl drɒp ɪkˌsperɪmənt/ US: /ˈmɪlɪkənz ˈɔɪl drɑːp ɪkˌsperɪmənt/	The experiment that provided evidence for quantized electric charge.
negative charge	UK: /ˈneɡətɪv tʃɑːdʒ/ US: /ˈneɡətɪv tʃɑːrdʒ/	One of the two types of electric charge, carried by electrons.
neutral body	UK: /ˈnjuːtrəl ˈbɒdi/ US: /ˈnuːtrəl ˈbɑːdi/	A body with zero net electric charge.
parallel plates	UK: /ˈpærəˌlel pleɪts/ US: /ˈperəˌlel pleɪts/	Two conducting plates used to produce an approximately uniform electric field.
permittivity	UK: /ˌpɜːmɪˈtɪvɪti/ US: /ˌpɝːmɪˈtɪvəti/	A property of a medium that determines its electric response and the strength of electric fields produced by charges within it.
point charge	UK: /pɔɪnt tʃɑːdʒ/ US: /pɔɪnt tʃɑːrdʒ/	An idealized charged body whose dimensions are negligible compared with the distances involved.
positive charge	UK: /ˈpɒzɪtɪv tʃɑːdʒ/ US: /ˈpɑːzətɪv tʃɑːrdʒ/	One of the two types of electric charge, conventionally carried by protons.
potential difference	UK: /pəˈtenʃəl ˈdɪf.ər.əns/ US: /pəˈtenʃəl ˈdɪf.ɚ.əns/	The energy transferred per unit charge between two points, $V=W/q$.
quantization of charge	UK: /ˌkwɒntaɪˈzeɪʃən əv tʃɑːdʒ/ US: /ˌkwɑːntaɪˈzeɪʃən əv tʃɑːrdʒ/	The fact that net charge occurs in discrete multiples of the elementary charge.
radial electric field	UK: /ˈreɪ.di.əl ɪˈlektrɪk fiːld/ US: /ˈreɪ.di.əl ɪˈlektrɪk fiːld/	An electric field whose field lines are directed radially towards or away from a central charge distribution.
right-hand grip rule	UK: /raɪt hænd ɡrɪp ruːl/ US: /raɪt hænd ɡrɪp ruːl/	A rule in which the right thumb points along conventional current and the curled fingers show the magnetic-field direction around it.
solenoid	UK: /ˈsəʊlənɔɪd/ US: /ˈsoʊlənɔɪd/	A long helical coil that produces an approximately uniform internal magnetic field.
solid charged conducting sphere	UK: /ˈsɒlɪd tʃɑːdʒd kənˈdʌktɪŋ sfɪə/ US: /ˈsɑːləd tʃɑːrdʒd kənˈdʌktɪŋ sfɪr/	An isolated charged spherical conductor; in electrostatic equilibrium its electric field is zero inside the conductor, its potential is constant there, and its external field is that of a point charge at its centre.
spherical conducting body	UK: /ˈsferɪkəl kənˈdʌktɪŋ ˈbɒdi/ US: /ˈsferɪkəl kənˈdʌktɪŋ ˈbɑːdi/	A conducting body with spherical symmetry; in electrostatic equilibrium its excess charge lies on its surface and the electric field inside the conducting material is zero.
test charge	UK: /test tʃɑːdʒ/ US: /test tʃɑːrdʒ/	An idealized small positive charge used to define or probe an electric field without significantly disturbing its sources.
uniform electric field	UK: /ˈjuːnɪˌfɔːm ɪˈlektrɪk fiːld/ US: /ˈjuːnəˌfɔːrm ɪˈlektrɪk fiːld/	An electric field whose vector has the same magnitude and direction throughout the region considered.

AHL

Term	Pronunciation	Definition
electric potential	UK: /ɪˈlektrɪk pəˈtenʃəl/ US: /ɪˈlektrɪk pəˈtenʃəl/	The electric potential energy per unit positive test charge at a point, with potential defined as zero at infinity.
electric potential energy	UK: /ɪˈlektrɪk pəˈtenʃəl ˈenədʒi/ US: /ɪˈlektrɪk pəˈtenʃəl ˈenɚdʒi/	The energy of a system due to the relative positions of its electric charges.
electronvolt	UK: /ɪˈlek.trɒnvəʊlt/ US: /ɪˈlek.trɑːnvoʊlt/	A unit of energy equal to the energy transferred when a charge of magnitude $e$ moves through a potential difference of one volt.
equipotential surface	UK: /ˌiːkwɪpəˈtenʃəl ˈsɜːfɪs/ US: /ˌiːkwɪpəˈtenʃəl ˈsɝːfəs/	A surface on which electric potential is constant.

D.3 Motion in electromagnetic fields

SL and HL

Term	Pronunciation	Definition
attractive force	UK: /əˈtræktɪv fɔːs/ US: /əˈtræktɪv fɔːrs/	A force drawing two bodies or wires towards each other.
cathode-ray tube	UK: /ˈkæθəʊd reɪ tjuːb/ US: /ˈkæθoʊd reɪ tuːb/	An evacuated tube in which an electron beam can be accelerated, deflected and made visible on a fluorescent screen.
charge-to-mass ratio	UK: /tʃɑːdʒ tə mæs ˈreɪʃiəʊ/ US: /tʃɑːrdʒ tuː mæs ˈreɪʃioʊ/	The algebraic electric charge of a particle divided by its mass; its magnitude is often inferred from deflection data.
charged particle	UK: /tʃɑːdʒd ˈpɑːtɪkəl/ US: /tʃɑːrdʒd ˈpɑːrtəkəl/	A particle with non-zero net electric charge.
circular path	UK: /ˈsɜːkjʊlə pɑːθ/ US: /ˈsɝːkjələr pæθ/	The path followed by a charged particle moving perpendicular to a uniform magnetic field when the magnetic force is the only resultant force.
crossed fields	UK: /krɒst fiːldz/ US: /krɔːst fiːldz/	Electric and magnetic fields arranged perpendicular to each other.
current-carrying conductor	UK: /ˈkʌrənt ˈkæriɪŋ kənˈdʌk.tə/ US: /ˈkɝːənt ˈkæriɪŋ kənˈdʌk.tɚ/	A conductor carrying electric current that may experience a magnetic force when placed in a magnetic field.
cyclotron	UK: /ˈsaɪklətrɒn/ US: /ˈsaɪklətrɑːn/	A particle accelerator that uses a perpendicular magnetic field and an alternating electric field to accelerate charged particles along an expanding path.
electric force	UK: /ɪˈlektrɪk fɔːs/ US: /ɪˈlektrɪk fɔːrs/	The force exerted on a charge by an electric field.
electron beam	UK: /ɪˈlek.trɒn biːm/ US: /ɪˈlek.trɑːn biːm/	A directed stream of electrons with a relatively narrow range of directions.
force per unit length	UK: /ˈfɔːs pər ˈjuːnɪt leŋθ/ US: /ˈfɔːrs pər ˈjuːnət leŋθ/	The force divided by the length over which it acts; for parallel current-carrying wires it is used to compare their magnetic interaction independently of the chosen wire length.
helical path	UK: /ˈhelɪkəl pɑːθ/ US: /ˈhelɪkəl pæθ/	A helical trajectory produced when a charged particle has velocity components both parallel and perpendicular to a uniform magnetic field.
magnetic deflection	UK: /mæɡˈnetɪk dɪˈflekʃən/ US: /mæɡˈnetɪk dɪˈflekʃən/	A change in a charged particle’s direction caused by magnetic force; in a static magnetic field its kinetic energy remains constant.
magnetic field strength	UK: /mæɡˈnetɪk fiːld streŋθ/ US: /mæɡˈnetɪk fiːld streŋθ/	The IB Physics name for the magnetic flux density $B$, which determines the magnetic force on a moving charge or a current-carrying conductor.
magnetic flux density	UK: /mæɡˈnetɪk flʌks ˈdensɪti/ US: /mæɡˈnetɪk flʌks ˈdensəti/	The standard SI name for the magnetic-field quantity $B$; for a uniform field normal to an area, $B=\Phi/A$, and its unit is the tesla.
magnetic force	UK: /mæɡˈnetɪk fɔːs/ US: /mæɡˈnetɪk fɔːrs/	The force exerted by a magnetic field on a moving charge, current or magnetic dipole.
mass spectrometer	UK: /mæs spekˈtrɒmɪtə/ US: /mæs spekˈtrɑːmətɚ/	An instrument that separates ions according to their mass-to-charge ratio using electric and magnetic fields.
orbital radius	UK: /ˈɔːbɪtəl ˈreɪ.di.əs/ US: /ˈɔːrbətəl ˈreɪ.di.əs/	The radius of a charged particle’s circular path in a magnetic field.
parabolic path	UK: /ˌpærəˈbɒlɪk pɑːθ/ US: /ˌperəˈbɑːlɪk pæθ/	The trajectory of a particle with uniform motion in one direction and constant acceleration in a perpendicular direction.
parallel currents	UK: /ˈpærəˌlel ˈkʌrənts/ US: /ˈperəˌlel ˈkɝːənts/	Currents flowing in parallel conductors.
permeability of free space	UK: /ˌpɜːmiəˈbɪləti əv friː speɪs/ US: /ˌpɝːmiəˈbɪləti əv friː speɪs/	The magnetic constant $\mu_0$ that appears in relationships for magnetic fields and forces in vacuum.
repulsive force	UK: /rɪˈpʌlsɪv fɔːs/ US: /riˈpʌlsɪv fɔːrs/	A force pushing two bodies or wires apart.
right-hand rule	UK: /raɪt hænd ruːl/ US: /raɪt hænd ruːl/	A rule for determining the magnetic-force direction on a moving positive charge from its velocity and the magnetic-field direction; the force reverses for a negative charge.
uniform electric field	UK: /ˈjuːnɪˌfɔːm ɪˈlektrɪk fiːld/ US: /ˈjuːnəˌfɔːrm ɪˈlektrɪk fiːld/	An electric field whose vector has the same magnitude and direction throughout the region considered.
uniform magnetic field	UK: /ˈjuːnɪˌfɔːm mæɡˈnetɪk fiːld/ US: /ˈjuːnəˌfɔːrm mæɡˈnetɪk fiːld/	A magnetic field whose vector has the same magnitude and direction throughout the region considered.
velocity selector	UK: /vəˈlɒsɪti sɪˈlektə/ US: /vəˈlɑːsəti sɪˈlektər/	A crossed-field device in which electric and magnetic forces cancel for particles of one selected speed.

D.4 Induction

AHL

Term	Pronunciation	Definition
alternating current	UK: /ˈɔːltəneɪtɪŋ ˈkʌrənt/ US: /ˈɔːltɚˌneɪtɪŋ ˈkɝːənt/	An electric current that reverses direction periodically.
alternating emf	UK: /ˈɔːltəneɪtɪŋ ˌiː em ˈef/ US: /ˈɔːltɚˌneɪtɪŋ ˌiː em ˈef/	An induced emf that reverses polarity periodically.
area normal	UK: /ˈeəriə ˈnɔːməl/ US: /ˈeriə ˈnɔːrməl/	A direction perpendicular to a surface, used to define the angle in the magnetic-flux equation.
back emf	UK: /bæk ˌiː em ˈef/ US: /bæk ˌiː em ˈef/	An induced emf whose polarity opposes the change in current or motion that produces it.
coil	UK: /kɔɪl/ US: /kɔɪl/	A conductor wound into one or more loops.
electromagnetic induction	UK: /ɪˌlektrəʊməɡˈnetɪk ɪnˈdʌk.ʃən/ US: /ˌɪˌlektroʊmæɡˈnetɪk ɪnˈdʌk.ʃən/	The production of an emf by a changing magnetic flux linkage.
energy conservation	UK: /ˈenədʒi ˌkɒnsəˈveɪʃən/ US: /ˈenɚdʒi ˌkɑːnsɚˈveɪʃən/	The total energy of an isolated system remains constant; in induction this requires the induced effect to oppose the change producing it.
Faraday’s law	UK: /ˈfærədeɪz lɔː/ US: /ˈfærədeɪz lɔː/	The induced emf around a circuit equals the negative rate of change of magnetic flux linkage.
flux linkage	UK: /flʌks ˈlɪŋkɪdʒ/ US: /flʌks ˈlɪŋkədʒ/	For a coil whose turns each have the same magnetic flux $\Phi$, the flux linkage is $N\Phi$.
frequency of rotation	UK: /ˈfriːkwənsi əv rəʊˈteɪʃən/ US: /ˈfriːkwənsi əv roʊˈteɪʃən/	The number of complete rotations per unit time; with other factors fixed, increasing it increases both the frequency and maximum magnitude of the emf induced in a rotating coil.
galvanometer	UK: /ˌɡælvəˈnɒmɪtə/ US: /ˌɡælvəˈnɑːmətɚ/	A sensitive instrument used to detect or measure small electric currents.
generator	UK: /ˈdʒen.ər.eɪ.tə/ US: /ˈdʒen.ər.eɪ.t̬ɚ/	A device that transfers mechanical energy to electrical energy by electromagnetic induction.
induced current	UK: /ɪnˈdjuːst ˈkʌrənt/ US: /ɪnˈduːst ˈkɝːənt/	A current caused by an induced emf in a closed circuit.
induced emf	UK: /ɪnˈdjuːst ˌiː em ˈef/ US: /ɪnˈduːst ˌiː em ˈef/	An electromotive force produced by electromagnetic induction.
Lenz’s law	UK: /ˈlentsɪz lɔː/ US: /ˈlentsɪz lɔː/	The direction of an induced current is such that its magnetic effect opposes the change in flux that produces it.
magnetic flux	UK: /mæɡˈnetɪk flʌks/ US: /mæɡˈnetɪk flʌks/	For a uniform magnetic field through a plane area, $\Phi=BA\cos\theta$, where $\theta$ is the angle between $\boldsymbol{B}$ and the area normal.
motional emf	UK: /ˈməʊʃənəl ˌiː em ˈef/ US: /ˈmoʊʃənəl ˌiː em ˈef/	An emf produced when a conductor moves through a magnetic field.
mutual induction	UK: /ˈmjuːtʃuəl ɪnˈdʌk.ʃən/ US: /ˈmjuːtʃuəl ɪnˈdʌk.ʃən/	The induction of an emf in one circuit by a changing current, and hence changing magnetic flux, in another circuit.
primary coil	UK: /ˈpraɪməri kɔɪl/ US: /ˈpraɪmeri kɔɪl/	The transformer coil connected to the input supply.
rectangular coil	UK: /rekˈtæŋ.ɡjə.lə kɔɪl/ US: /rekˈtæŋ.ɡjə.lɚ kɔɪl/	A coil whose turns have rectangular shape.
relative motion	UK: /ˈrelətɪv ˈməʊʃən/ US: /ˈrelətɪv ˈmoʊʃən/	Motion of a conductor and magnetic field relative to each other.
rotating coil	UK: /rəʊˈteɪtɪŋ kɔɪl/ US: /ˈroʊˌteɪtɪŋ kɔɪl/	A coil rotating in a magnetic field to produce changing flux.
secondary coil	UK: /ˈsekəndəri kɔɪl/ US: /ˈsekənderi kɔɪl/	The transformer coil across which the output emf is induced.
self-induction	UK: /self ɪnˈdʌk.ʃən/ US: /self ɪnˈdʌk.ʃən/	Induction in a circuit caused by a change in its own current.
sinusoidally varying emf	UK: /ˌsaɪnəˈsɔɪdəli ˈveəriɪŋ ˌiː em ˈef/ US: /ˌsaɪnəˈsɔɪdəli ˈveriɪŋ ˌiː em ˈef/	An emf whose instantaneous value varies as a sine or cosine function of time, as produced by a coil rotating uniformly in a uniform magnetic field.
slip ring	UK: /slɪp rɪŋ/ US: /slɪp rɪŋ/	A conducting ring that maintains electrical contact with a rotating coil without reversing the connection each half-turn.
straight conductor	UK: /streɪt kənˈdʌk.tə/ US: /streɪt kənˈdʌk.tɚ/	A conductor modelled as straight over the relevant length; moving it across a uniform magnetic field can produce a motional emf.
time-varying magnetic field	UK: /ˈtaɪm ˌveəriɪŋ mæɡˈnetɪk fiːld/ US: /ˈtaɪm ˌveriɪŋ mæɡˈnetɪk fiːld/	A magnetic field whose magnitude, direction or both change with time and which can therefore change the magnetic flux through a circuit.
transformer	UK: /trænsˈfɔːmə/ US: /trænsˈfɔːrmɚ/	A device that uses mutual induction between coils to increase or decrease an alternating potential difference.
weber	UK: /ˈveɪbə/ US: /ˈveɪbər/	The SI unit of magnetic flux.

E.1 Structure of the atom

SL and HL

Term	Pronunciation	Definition
absorption spectrum	UK: /əbˈzɔːpʃən ˈspektrəm/ US: /əbˈzɔːrpʃən ˈspektrəm/	A spectrum containing dark lines or bands at wavelengths absorbed from incident radiation.
alpha particle	UK: /ˈælfə ˈpɑːtɪkəl/ US: /ˈælfə ˈpɑːrtəkəl/	A helium-4 nucleus consisting of two protons and two neutrons, with charge $+2e$.
atom	UK: /ˈætəm/ US: /ˈætəm/	The smallest unit of an element that retains its chemical identity, consisting of a nucleus with bound electrons.
atomic transition	UK: /əˈtɒmɪk trænˈzɪʃən/ US: /əˈtɑːmɪk trænˈzɪʃən/	A change between atomic energy levels; in a radiative transition, the absorbed or emitted photon energy equals the energy-level difference.
discrete energy level	UK: /dɪˈskriːt ˈenədʒi ˌlevəl/ US: /dɪˈskriːt ˈenɚdʒi ˌlevəl/	One of a separated set of allowed energy values for an atom or nucleus.
electron	UK: /ɪˈlek.trɒn/ US: /ɪˈlek.trɑːn/	An elementary particle with electric charge $-e$.
emission spectrum	UK: /ɪˈmɪʃən ˈspektrəm/ US: /ɪˈmɪʃən ˈspektrəm/	A spectrum of discrete wavelengths emitted by excited atoms.
energy level	UK: /ˈenədʒi ˈlevəl/ US: /ˈenɚdʒi ˈlevəl/	One of the discrete energy values permitted for a system such as an atom or nucleus.
energy-level diagram	UK: /ˈenədʒi ˈlevəl ˈdaɪəɡræm/ US: /ˈenɚdʒi ˈlevəl ˈdaɪəɡræm/	A diagram showing the allowed discrete energies of a system and possible transitions between them.
excited state	UK: /ɪkˈsaɪtɪd steɪt/ US: /ɪkˈsaɪtɪd steɪt/	An allowed state with energy greater than the ground-state energy.
fluorescent screen	UK: /flʊəˈresənt skriːn/ US: /flɔːˈresənt skriːn/	A screen coated with a material that emits visible light when struck by suitable radiation or charged particles.
Geiger-Marsden-Rutherford experiment	UK: /ˈɡaɪɡə ˈmɑːzdən ˈrʌðəfəd ɪkˈsperɪmənt/ US: /ˈɡaɪɡɚ ˈmɑːrzdən ˈrʌðɚfɚd ɪkˈsperəmənt/	The alpha-particle scattering experiment whose results showed that an atom’s positive charge and most of its mass are concentrated in a small nucleus.
ground state	UK: /ɡraʊnd steɪt/ US: /ɡraʊnd steɪt/	The lowest-energy allowed state of a system.
line spectrum	UK: /laɪn ˈspektrəm/ US: /laɪn ˈspektrəm/	A spectrum containing discrete wavelengths produced by transitions between discrete energy levels.
neutron	UK: /ˈnjuːtrɒn/ US: /ˈnuːtrɑːn/	An electrically neutral nucleon in an atomic nucleus.
nuclear notation	UK: /ˈnjuː.kli.ə nəʊˈteɪʃən/ US: /ˈnuː.kli.ɚ noʊˈteɪʃən/	The symbolic notation showing proton number, nucleon number and element.
nucleon	UK: /ˈnjuːkliɒn/ US: /ˈnuːkliɑːn/	A proton or neutron.
nucleon number	UK: /ˈnjuːkliɒn ˈnʌmbə/ US: /ˈnuːkliɑːn ˈnʌmbɚ/	The total number of protons and neutrons in a nucleus.
nucleus	UK: /ˈnjuː.kli.əs/ US: /ˈnuːkliəs/	The small, dense, positively charged central part of an atom, containing one or more protons and, except for hydrogen-1, neutrons.
photon	UK: /ˈfəʊtɒn/ US: /ˈfoʊˌtɑːn/	A quantum of electromagnetic radiation with energy $E=hf$ and momentum $p=h/\lambda$.
proton	UK: /ˈprəʊtɒn/ US: /ˈproʊtɑːn/	A positively charged nucleon in an atomic nucleus.
proton number	UK: /ˈprəʊtɒn ˈnʌmbə/ US: /ˈproʊtɑːn ˈnʌmbɚ/	The number of protons in a nucleus.
Rutherford scattering	UK: /ˈrʌðəfəd ˈskætərɪŋ/ US: /ˈrʌðərfərd ˈskætɚɪŋ/	Scattering of alpha particles by nuclei, revealing concentrated positive charge.
scattering angle	UK: /ˈskætərɪŋ ˈæŋɡəl/ US: /ˈskætərɪŋ ˈæŋɡəl/	The angle between a particle’s incident direction and its direction after scattering.

AHL

Term	Pronunciation	Definition
Bohr model	UK: /bɔː ˈmɒdəl/ US: /bɔːr ˈmɑːdəl/	An atomic model with electrons in permitted quantized orbits.
Bohr radius	UK: /ˈbɔː ˈreɪ.di.əs/ US: /ˈbɔːr ˈreɪ.di.əs/	The radius of the lowest-energy allowed orbit in the Bohr model of hydrogen.
distance of closest approach	UK: /ˈdɪstəns əv ˈkləʊsɪst əˈprəʊtʃ/ US: /ˈdɪstəns əv ˈkloʊsəst əˈproʊtʃ/	The minimum separation reached in a head-on repulsive scattering event.
hydrogen atom	UK: /ˈhaɪdrədʒən ˈætəm/ US: /ˈhaɪdrədʒən ˈætəm/	An atom whose nucleus contains one proton and whose neutral state contains one electron.
ionization energy	UK: /ˌaɪənaɪˈzeɪʃən ˈenədʒi/ US: /ˌaɪənaɪˈzeɪʃən ˈenɚdʒi/	The minimum energy required to remove an electron from an atom in a specified state to infinity with zero kinetic energy.
nuclear density	UK: /ˈnjuː.kli.ə ˈdensɪti/ US: /ˈnuː.kli.ɚ ˈdensəti/	The mass of a nucleus divided by its volume; the nuclear-radius relationship implies that it is approximately independent of nucleon number.
nuclear radius	UK: /ˈnjuː.kli.ə ˈreɪ.di.əs/ US: /ˈnuː.kli.ɚ ˈreɪ.di.əs/	The effective radius of a nucleus.
quantized angular momentum	UK: /ˈkwɒntaɪzd ˈæŋ.ɡjə.lə məˈmentəm/ US: /ˈkwɑːntaɪzd ˈæŋ.ɡjə.lɚ moʊˈmentəm/	Angular momentum restricted to discrete permitted values.

E.2 Quantum physics

AHL

Term	Pronunciation	Definition
classical wave theory	UK: /ˈklæsɪkəl weɪv ˈθɪəri/ US: /ˈklæsɪkəl weɪv ˈθɪri/	The non-quantized wave description of electromagnetic radiation.
collecting electrode	UK: /kəˈlektɪŋ ɪˈlektrəʊd/ US: /kəˈlektɪŋ ɪˈlektroʊd/	An electrode arranged to collect photoelectrons in a photoelectric-effect apparatus.
Compton scattering	UK: /ˈkɒmptən ˈskætərɪŋ/ US: /ˈkɑːmptən ˈskætɚɪŋ/	Scattering of a photon by an electron in which the photon emerges with a longer wavelength.
de Broglie wavelength	UK: /də brɔɪ ˈweɪv.leŋθ/ US: /də brɔɪ ˈweɪv.leŋθ/	The wavelength associated with a particle of momentum $p$, given by $\lambda=h/p$.
electron diffraction	UK: /ɪˈlek.trɒn dɪˈfrækʃən/ US: /ɪˈlek.trɑːn dɪˈfrækʃən/	Diffraction of electrons, providing evidence for the wave nature of matter.
incident photon	UK: /ˈɪn.sɪ.dənt ˈfəʊtɒn/ US: /ˈɪn.sɪ.dənt ˈfoʊtɑːn/	A photon approaching and interacting with a target particle or material.
matter wave	UK: /ˈmætə weɪv/ US: /ˈmætɚ weɪv/	The wave behaviour associated with a material particle.
maximum kinetic energy	UK: /ˈmæksɪməm kɪˈnetɪk ˈenədʒi/ US: /ˈmæksəməm kɪˈnetɪk ˈenɚdʒi/	The greatest kinetic energy among emitted photoelectrons.
particle diffraction	UK: /ˈpɑːtɪkəl dɪˈfrækʃən/ US: /ˈpɑːrtəkəl dɪˈfrækʃən/	Diffraction shown by particles when their wavelength is comparable to structural spacing.
photocathode	UK: /ˌfəʊtəʊˈkæθəʊd/ US: /ˌfoʊtoʊˈkæθoʊd/	A light-sensitive cathode that emits electrons by the photoelectric effect.
photocell	UK: /ˈfəʊtəʊsel/ US: /ˈfoʊtoʊsel/	A light-sensitive device whose electrical response depends on illumination; a photoelectric-effect photocell contains emitting and collecting electrodes.
photoelectric effect	UK: /ˌfəʊtəʊɪˈlektrɪk ɪˈfekt/ US: /ˌfoʊtoʊɪˈlektrɪk ɪˈfekt/	The emission of electrons from a material after absorption of electromagnetic radiation.
photoelectron	UK: /ˌfəʊtəʊɪˈlek.trɒn/ US: /ˌfoʊtoʊɪˈlek.trɑːn/	An electron emitted by the photoelectric effect.
photon momentum	UK: /ˈfəʊtɒn məˈmentəm/ US: /ˈfoʊtɑːn moʊˈmentəm/	The momentum carried by a photon, with magnitude $p=h/\lambda=E/c$.
Planck constant	UK: /plæŋk ˈkɒnstənt/ US: /plæŋk ˈkɑːnstənt/	The universal constant relating photon energy to frequency and wavelength to momentum.
recoiling electron	UK: /rɪˈkɔɪlɪŋ ɪˈlek.trɒn/ US: /rɪˈkɔɪlɪŋ ɪˈlek.trɑːn/	An electron that gains momentum and kinetic energy when a photon scatters from it.
scattered photon	UK: /ˈskætəd ˈfəʊtɒn/ US: /ˈskætɚd ˈfoʊtɑːn/	A photon whose direction and, in Compton scattering, wavelength have changed through interaction with an electron.
stopping potential	UK: /ˈstɒpɪŋ pəˈtenʃəl/ US: /ˈstɑːpɪŋ pəˈtenʃəl/	The minimum reverse potential difference that reduces the photocurrent to zero by preventing even the most energetic photoelectrons from reaching the collector.
threshold frequency	UK: /ˈθreˌʃəʊld ˈfriːkwənsi/ US: /ˈθreˌʃoʊld ˈfriːkwənsi/	For a specified material surface, the minimum incident-radiation frequency that can produce photoelectron emission.
wave-particle duality	UK: /weɪv ˈpɑːtɪkəl djuːˈælɪti/ US: /weɪv ˈpɑːrtəkəl duˈæləti/	The quantum behaviour in which light and matter show wave-like or particle-like features according to the experimental arrangement; neither classical description alone is sufficient.
wavelength shift	UK: /ˈweɪv.leŋθ ʃɪft/ US: /ˈweɪv.leŋθ ʃɪft/	The difference between final and initial photon wavelength.
work function	UK: /wɜːk ˈfʌŋkʃən/ US: /wɝːk ˈfʌŋkʃən/	The minimum energy required to remove an electron from the surface of a material.

E.3 Radioactive decay

SL and HL

Term	Pronunciation	Definition
activity	UK: /ækˈtɪvɪti/ US: /ækˈtɪvəti/	The mean number of nuclear decays per unit time in a radioactive sample.
alpha decay	UK: /ˈælfə dɪˈkeɪ/ US: /ˈælfə dɪˈkeɪ/	Decay in which a nucleus emits an alpha particle.
alpha particle	UK: /ˈælfə ˈpɑːtɪkəl/ US: /ˈælfə ˈpɑːrtəkəl/	A helium-4 nucleus consisting of two protons and two neutrons, with charge $+2e$.
antineutrino	UK: /ˌæntinjuːˈtriːnəʊ/ US: /ˌæntinuːˈtriːnoʊ/	The electrically neutral antiparticle of the neutrino, emitted in beta-minus decay.
background radiation	UK: /ˈbækˌɡraʊnd ˌreɪdɪˈeɪʃən/ US: /ˈbækˌɡraʊnd ˌreɪdiˈeɪʃən/	Ionizing radiation detected from environmental and instrumental sources other than the source being investigated.
becquerel	UK: /ˌbekəˈrel/ US: /ˌbekəˈrel/	The SI unit of activity equal to one decay per second.
beta particle	UK: /ˈbiːtə ˈpɑːtɪkəl/ US: /ˈbeɪtə ˈpɑːrtəkəl/	A high-speed electron or positron emitted in beta decay.
beta-minus decay	UK: /ˈbiːtə ˈmaɪnəs dɪˈkeɪ/ US: /ˈbeɪtə ˈmaɪnəs dɪˈkeɪ/	Decay in which a neutron changes into a proton, electron and antineutrino.
beta-plus decay	UK: /ˈbiːtə plʌs dɪˈkeɪ/ US: /ˈbeɪtə plʌs dɪˈkeɪ/	Decay in which a proton changes into a neutron, positron and neutrino.
binding energy	UK: /ˈbaɪndɪŋ ˈenədʒi/ US: /ˈbaɪndɪŋ ˈenɚdʒi/	The positive energy required to separate a bound system into specified free constituents.
binding energy per nucleon	UK: /ˈbaɪndɪŋ ˈenədʒi pə ˈnjuːkliɒn/ US: /ˈbaɪndɪŋ ˈenɚdʒi pɚ ˈnuːkliɑːn/	The total binding energy of a nucleus divided by its nucleon number.
cloud chamber	UK: /klaʊd ˈtʃeɪmbə/ US: /klaʊd ˈtʃeɪmbɚ/	A detector in which charged particles leave visible condensation tracks in a supersaturated vapour.
corrected count rate	UK: /kəˈrektɪd kaʊnt reɪt/ US: /kəˈrektɪd kaʊnt reɪt/	The measured count rate after subtracting the background count rate.
count rate	UK: /kaʊnt reɪt/ US: /kaʊnt reɪt/	The number of detector counts recorded per unit time.
daughter nuclide	UK: /ˈdɔːtə ˈnjuːklaɪd/ US: /ˈdɔːtɚ ˈnuːklaɪd/	The nuclide produced directly by the radioactive decay of a parent nuclide.
dosimeter	UK: /dəʊˈsɪmɪtə/ US: /doʊˈsɪmətɚ/	A device used to measure the ionizing-radiation dose received by a person or object over time.
gamma decay	UK: /ˈɡæmə dɪˈkeɪ/ US: /ˈɡæmə dɪˈkeɪ/	A nuclear transition that emits a gamma photon without changing nucleon or proton number.
gamma radiation	UK: /ˈɡæmə ˌreɪdɪˈeɪʃən/ US: /ˈɡæmə ˌreɪdiˈeɪʃən/	High-energy electromagnetic radiation emitted in nuclear transitions.
Geiger-Müller tube	UK: /ˈɡaɪɡə ˈmʊlə tjuːb/ US: /ˈɡaɪɡɚ ˈmʊlɚ tuːb/	A gas-filled detector that produces an electrical pulse when ionizing radiation causes ionization in the tube.
half-life	UK: /hɑːf laɪf/ US: /hæf laɪf/	The time for the expected number of undecayed nuclei, or the activity of a large sample, to fall to half its initial value.
ionizing power	UK: /ˈaɪənaɪzɪŋ ˈpaʊə/ US: /ˈaɪənaɪzɪŋ ˈpaʊɚ/	The ability of radiation to produce ions in matter.
ionizing radiation	UK: /ˈaɪənaɪzɪŋ ˌreɪdɪˈeɪʃən/ US: /ˈaɪənaɪzɪŋ ˌreɪdiˈeɪʃən/	Radiation with sufficient energy per particle or photon to remove electrons from atoms or molecules.
isotope	UK: /ˈaɪsəˌtəʊp/ US: /ˈaɪsətoʊp/	One of two or more nuclides with the same proton number but different neutron numbers.
mass defect	UK: /mæs ˈdiːfekt/ US: /mæs ˈdiːfekt/	The sum of the rest masses of the separated constituent nucleons minus the rest mass of the bound nucleus.
mass-energy equivalence	UK: /mæs ˈenədʒi ɪˈkwɪvələns/ US: /mæs ˈenɚdʒi ɪˈkwɪvələns/	The equivalence of mass and energy expressed by $E=mc^2$.
neutrino	UK: /njuːˈtriːnəʊ/ US: /nuːˈtriːnoʊ/	An electrically neutral elementary particle with very small mass, emitted in beta-plus decay.
nuclear mass	UK: /ˈnjuː.kli.ə mæs/ US: /ˈnuː.kli.ɚ mæs/	The mass of a nucleus, expressible in kilograms, unified atomic mass units or energy-equivalent units such as $\text{MeV}\,c^{-2}$.
nuclide	UK: /ˈnjuːklaɪd/ US: /ˈnuːklaɪd/	A species of nucleus specified by its proton number and neutron number.
parent nuclide	UK: /ˈpeərənt ˈnjuːklaɪd/ US: /ˈperənt ˈnuːklaɪd/	The radioactive nuclide that undergoes decay to produce a daughter nuclide.
penetrating power	UK: /ˈpenɪˌtreɪtɪŋ ˈpaʊə/ US: /ˈpenəˌtreɪtɪŋ ˈpaʊɚ/	The ability of radiation to pass through matter.
positron	UK: /ˈpɒzɪtrɒn/ US: /ˈpɑːzɪtrɑːn/	The positively charged antiparticle of the electron.
radiation detector	UK: /ˌreɪdɪˈeɪʃən dɪˈtektə/ US: /ˌreɪdiˈeɪʃən dɪˈtektɚ/	A device that produces a measurable response when radiation deposits energy in it.
radioactive dating	UK: /ˌreɪdɪəʊˈæktɪv ˈdeɪtɪŋ/ US: /ˌreɪdioʊˈæktɪv ˈdeɪtɪŋ/	Determining the age of a sample from measured parent or daughter nuclide quantities and a known decay law.
radioactive decay	UK: /ˌreɪdɪəʊˈæktɪv dɪˈkeɪ/ US: /ˌreɪdioʊˈæktɪv dɪˈkeɪ/	The spontaneous and random transformation of an unstable nucleus into another state or nuclide.
radioactive tracer	UK: /ˌreɪdɪəʊˈæktɪv ˈtreɪsə/ US: /ˌreɪdioʊˈæktɪv ˈtreɪsɚ/	A radioactive substance used to follow the movement or distribution of material by detecting its radiation.
scintillation detector	UK: /ˌsɪntɪˈleɪʃən dɪˈtektə/ US: /ˌsɪntəˈleɪʃən dɪˈtektɚ/	A detector in which radiation produces flashes of light that are converted into electrical pulses.
strong nuclear force	UK: /strɒŋ ˈnjuː.kli.ə fɔːs/ US: /strɔːŋ ˈnuː.kli.ɚ fɔːrs/	A short-range attractive force between nucleons.
unified atomic mass unit	UK: /ˈjuːnɪfaɪd əˈtɒmɪk mæs ˈjuːnɪt/ US: /ˈjuːnəfaɪd əˈtɑːmɪk mæs ˈjuːnət/	A unit of mass, symbol $\mathrm u$, defined as one twelfth of the mass of a neutral carbon-12 atom in its ground state.

AHL

Term	Pronunciation	Definition
continuous beta spectrum	UK: /kənˈtɪn.ju.əs ˈbiːtə ˈspektrəm/ US: /kənˈtɪn.ju.əs ˈbeɪtə ˈspektrəm/	The continuous distribution of beta-particle energies, providing evidence that a neutrino or antineutrino carries away energy in beta decay.
decay constant	UK: /dɪˈkeɪ ˈkɒnstənt/ US: /dɪˈkeɪ ˈkɑːnstənt/	The constant decay probability per unit time for an individual unstable nucleus in the exponential-decay model.
discrete gamma spectrum	UK: /dɪˈskriːt ˈɡæmə ˈspektrəm/ US: /dɪˈskriːt ˈɡæmə ˈspektrəm/	A set of distinct gamma-ray energies from nuclear transitions.
exponential decay	UK: /ˌek.spəˈnen.ʃəl dɪˈkeɪ/ US: /ˌek.spoʊˈnen.ʃəl dɪˈkeɪ/	Decay in which the rate is proportional to the number of undecayed nuclei.
neutron-to-proton ratio	UK: /ˈnjuːtrɒn tə ˈprəʊtɒn ˈreɪʃiəʊ/ US: /ˈnuːtrɑːn tuː ˈproʊtɑːn ˈreɪʃioʊ/	The ratio of neutron number to proton number in a nucleus.
nuclear stability	UK: /ˈnjuː.kli.ə stəˈbɪlɪti/ US: /ˈnuː.kli.ɚ stəˈbɪlɪti/	The condition in which a nucleus does not undergo spontaneous radioactive decay.

E.4 Fission

SL and HL

Term	Pronunciation	Definition
chain reaction	UK: /tʃeɪn rɪˈækʃən/ US: /tʃeɪn riˈækʃən/	A sequence in which neutrons released by one fission generation induce fissions in later generations.
control rod	UK: /kənˈtrəʊl rɒd/ US: /kənˈtroʊl rɑːd/	A neutron-absorbing reactor component inserted or withdrawn to control the fission rate.
coolant	UK: /ˈkuːlənt/ US: /ˈkuːlənt/	A fluid that transfers thermal energy away from a reactor core.
criticality	UK: /ˌkrɪtɪˈkæləti/ US: /ˌkrɪtɪˈkæləti/	The state of a fission chain reaction: subcritical if it decreases, critical if it remains steady, and supercritical if it increases.
energy release	UK: /ˈenədʒi rɪˈliːs/ US: /ˈenɚdʒi riˈliːs/	Energy transferred from a decrease $\Delta m$ in total rest mass, $\Delta E=\Delta m c^2$, appearing as kinetic energy, radiation or other forms.
fissile material	UK: /ˈfɪsaɪl məˈtɪəriəl/ US: /ˈfɪsəl məˈtɪriəl/	A material containing nuclides capable of sustaining a chain reaction with neutrons of the relevant energies.
fission fragment	UK: /ˈfɪʃən ˈfræɡmənt/ US: /ˈfɪʃən ˈfræɡmənt/	One of the smaller nuclei produced in fission.
fission product	UK: /ˈfɪʃən ˈprɒdʌkt/ US: /ˈfɪʃən ˈprɑːdʌkt/	A nuclide produced by fission, including the primary fragments and their radioactive decay products.
heat exchanger	UK: /hiːt eksˈtʃeɪndʒə/ US: /hiːt ɪksˈtʃeɪndʒɚ/	A device that transfers thermal energy between fluids without mixing them.
moderator	UK: /ˈmɒdəˌreɪtə/ US: /ˈmɑːdɚˌeɪtɚ/	A reactor material that slows neutrons, mainly by collisions, while absorbing relatively few of them.
neutron absorption	UK: /ˈnjuːtrɒn əbˈzɔːpʃən/ US: /ˈnuːtrɑːn əbˈzɔːrpʃən/	A nuclear process in which a nucleus captures a neutron.
neutron-induced fission	UK: /ˈnjuːtrɒn ɪnˈdjuːst ˈfɪʃən/ US: /ˈnuːtrɑːn ɪnˈduːst ˈfɪʃən/	Fission initiated when a nucleus absorbs a neutron.
nuclear fission	UK: /ˈnjuː.kli.ə ˈfɪʃən/ US: /ˈnuː.kli.ɚ ˈfɪʃən/	The splitting of a heavy nucleus into two lighter nuclei, usually with neutrons and energy released.
nuclear fuel	UK: /ˈnjuː.kli.ə ˈfjuːəl/ US: /ˈnuː.kli.ɚ ˈfjuːəl/	Material containing nuclides used as a source of nuclear energy in a reactor, principally through fission.
nuclear power plant	UK: /ˈnjuː.kli.ə ˈpaʊə plɑːnt/ US: /ˈnuː.kli.ɚ ˈpaʊɚ plænt/	A facility that uses controlled nuclear fission to provide thermal energy for electrical power generation.
nuclear reactor	UK: /ˈnjuː.kli.ə riˈæk.tə/ US: /ˈnuː.kli.ɚ riˈæk.tɚ/	A system in which a controlled fission chain reaction releases energy.
radioactive waste	UK: /ˌreɪdɪəʊˈæktɪv weɪst/ US: /ˌreɪdioʊˈæktɪv weɪst/	Radioactive material requiring controlled handling, storage or disposal.
reactor core	UK: /riˈæk.tə kɔː/ US: /riˈæk.tɚ kɔːr/	The region of a nuclear reactor containing the fuel and supporting the controlled fission chain reaction.
shielding	UK: /ˈʃiːldɪŋ/ US: /ˈʃiːldɪŋ/	Material used to reduce exposure to ionizing radiation.
spontaneous fission	UK: /spɒnˈteɪnɪəs ˈfɪʃən/ US: /spɑːnˈteɪniəs ˈfɪʃən/	Fission occurring without absorption of an incident neutron.

E.5 Fusion and stars

SL and HL

Term	Pronunciation	Definition
arcsecond	UK: /ˈɑːksekənd/ US: /ˈɑːrksekənd/	An angular unit equal to one three-thousand-six-hundredth of a degree.
astronomical unit	UK: /ˌæstrəˈnɒmɪkəl ˈjuːnɪt/ US: /ˌæstrəˈnɑːmɪkəl ˈjuːnət/	A unit of length defined as exactly $149\,597\,870\,700\ \mathrm{m}$.
black hole	UK: /blæk həʊl/ US: /blæk hoʊl/	A compact object whose gravitational field is strong enough that no signal from within its event horizon can reach the outside universe.
element formation	UK: /ˈelɪmənt fɔːˈmeɪʃən/ US: /ˈeləmənt fɔːrˈmeɪʃən/	The production of chemical elements through nuclear reactions.
gravitational force	UK: /ˌɡrævɪˈteɪʃənəl fɔːs/ US: /ˌɡrævɪˈteɪʃənəl fɔːrs/	The attractive force between masses.
Hertzsprung-Russell diagram	UK: /ˈhɜːtsprʊŋ ˈrʌsəl ˈdaɪəɡræm/ US: /ˈhɝːtsprʊŋ ˈrʌsəl ˈdaɪəɡræm/	A graph classifying stars by luminosity and surface temperature.
high-mass star	UK: /haɪ mæs stɑː/ US: /haɪ mæs stɑːr/	A star whose comparatively large initial mass leads to high core temperature and an evolutionary path that can end in core collapse.
hydrostatic equilibrium	UK: /ˌhaɪdrəʊˈstætɪk ˌiːkwɪˈlɪbrɪəm/ US: /ˌhaɪdroʊˈstætɪk ˌiːkwəˈlɪbriəm/	The state of a star in which outward thermal or radiation pressure balances inward pressure due to gravitational forces.
instability strip	UK: /ˌɪnstəˈbɪlɪti strɪp/ US: /ˌɪnstəˈbɪlɪti strɪp/	A region of the HR diagram containing pulsating variable stars.
light-year	UK: /laɪt jɪə/ US: /laɪt jɪr/	The distance travelled by light in vacuum in one year, approximately $9.46\times10^{15}\ \mathrm{m}$.
line of constant radius	UK: /laɪn əv ˈkɒnstənt ˈreɪ.di.əs/ US: /laɪn əv ˈkɑːnstənt ˈreɪ.di.əs/	A line on an HR diagram joining stellar states with the same radius, as determined from luminosity and surface temperature.
low-mass star	UK: /ləʊ mæs stɑː/ US: /loʊ mæs stɑːr/	A star whose comparatively small initial mass leads to an evolution that ends without core-collapse supernova.
main sequence	UK: /meɪn ˈsiːkwəns/ US: /meɪn ˈsiːkwəns/	The band on the Hertzsprung–Russell diagram occupied by stars that sustain hydrogen fusion in their cores.
neutron star	UK: /ˈnjuːtrɒn stɑː/ US: /ˈnuːtrɑːn stɑːr/	A compact stellar remnant composed predominantly of neutron-rich matter after the core collapse of a sufficiently massive star.
nuclear fusion	UK: /ˈnjuː.kli.ə ˈfjuːʒən/ US: /ˈnuː.kli.ɚ ˈfjuːʒən/	A nuclear reaction in which light nuclei combine to form heavier nuclei, with energy released when the products have lower total rest mass.
parsec	UK: /ˈpɑːsek/ US: /ˈpɑːrsek/	The distance at which one astronomical unit subtends an angle of one arcsecond, approximately 3.26 light-years.
planetary nebula	UK: /ˈplænɪtəri ˈnebjʊlə/ US: /ˈplænəteri ˈnebjələ/	An expanding shell of gas ejected by a low- or intermediate-mass star near the end of its evolution.
protostar	UK: /ˈprəʊtəʊstɑː/ US: /ˈproʊtoʊstɑːr/	A forming star before sustained hydrogen fusion begins.
radiation pressure	UK: /ˌreɪdɪˈeɪʃən ˈpreʃə/ US: /ˌreɪdiˈeɪʃən ˈpreʃɚ/	The normal force per unit area produced when electromagnetic radiation transfers momentum to matter.
red giant	UK: /red ˈdʒaɪənt/ US: /red ˈdʒaɪənt/	A cool luminous evolved star with a large radius.
red supergiant	UK: /red ˈsuːpədʒaɪənt/ US: /red ˈsuːpɚdʒaɪənt/	A cool, highly luminous evolved high-mass star with a very large radius.
stellar core	UK: /ˈstelə kɔː/ US: /ˈstelɚ kɔːr/	The central region of a star, where density and temperature may be sufficient for fusion.
stellar evolution	UK: /ˈstelə ˌiːvəˈluːʃən/ US: /ˈstelɚ ˌevəˈluːʃən/	The sequence of changes in a star over its lifetime.
stellar fusion	UK: /ˈstelə ˈfjuːʒən/ US: /ˈstelɚ ˈfjuːʒən/	Fusion reactions that supply energy inside stars.
stellar luminosity	UK: /ˈstelə ˌluːmɪˈnɒsɪti/ US: /ˈstelɚ ˌluːməˈnɑːsəti/	The total power emitted by a star.
stellar mass	UK: /ˈstelə mæs/ US: /ˈstelər mæs/	The mass of a star, a principal factor determining its luminosity, lifetime and evolutionary pathway.
stellar parallax	UK: /ˈstelə ˈpærəlæks/ US: /ˈstelɚ ˈpærəlæks/	Half the apparent annual angular shift of a nearby star relative to distant background objects, as viewed from opposite sides of Earth’s orbit.
stellar radius	UK: /ˈstelə ˈreɪ.di.əs/ US: /ˈstelɚ ˈreɪ.di.əs/	The effective radius of a star.
stellar remnant	UK: /ˈstelə ˈremnənt/ US: /ˈstelɚ ˈremnənt/	The compact object left after a star ends its active evolutionary stages.
stellar spectrum	UK: /ˈstelə ˈspektrəm/ US: /ˈstelɚ ˈspektrəm/	The distribution of a star’s emitted intensity with wavelength.
supergiant	UK: /ˈsuːpədʒaɪənt/ US: /ˈsuːpərdʒaɪənt/	An extremely luminous star with a very large radius.
supernova	UK: /ˌsuːpəˈnəʊvə/ US: /ˌsuːpɚˈnoʊvə/	A stellar explosion that produces a rapid, very large increase in luminosity and ejects stellar material.
surface temperature	UK: /ˈsɜːfɪs ˈtemprətʃə/ US: /ˈsɝːfəs ˈtemprətʃɚ/	The effective temperature characterizing radiation from a star’s surface.
thermal pressure	UK: /ˈθɜːməl ˈpreʃə/ US: /ˈθɝːməl ˈpreʃɚ/	Pressure in stellar matter arising from the random thermal motion and interactions of its particles.
white dwarf	UK: /waɪt dwɔːf/ US: /waɪt dwɔːrf/	A compact stellar remnant supported primarily by electron degeneracy pressure.

Physics toolkit and inquiry terminology

This section covers the core experimental-design, data-processing, conclusion and evaluation terminology used in the Tools and Inquiry process of the current IB Physics Guide.

Term	Pronunciation	Definition
approximation	UK: /əˌprɒksɪˈmeɪʃən/ US: /əˌprɑːksəˈmeɪʃən/	A value or relationship sufficiently close to the exact one for the stated purpose.
assumption	UK: /əˈsʌmpʃən/ US: /əˈsʌmpʃən/	A condition accepted for a model or analysis whose validity and effect on the conclusion must be considered.
bar chart	UK: /ˈbɑː tʃɑːt/ US: /ˈbɑːr tʃɑːrt/	A chart using separated rectangular bars to compare values for discrete categories.
calibration	UK: /ˌkælɪˈbreɪʃən/ US: /ˌkæləˈbreɪʃən/	The comparison of an instrument’s readings with known reference values to establish the relationship between indication and measured quantity and identify any correction.
computer modelling	UK: /kəmˈpjuːtə ˈmɒdəlɪŋ/ US: /kəmˈpjuːtər ˈmɑːdəlɪŋ/	The construction or use of computational representations to explore, explain or predict a physical system.
continuous variable	UK: /kənˈtɪn.ju.əs ˈveə.ri.ə.bəl/ US: /kənˈtɪn.ju.əs ˈver.i.ə.bəl/	A variable that can take any value within a permitted interval.
control variable	UK: /kənˈtrəʊl ˈveə.ri.ə.bəl/ US: /kənˈtroʊl ˈver.i.ə.bəl/	A variable kept constant so that it does not confound the relationship under investigation.
database	UK: /ˈdeɪtəbeɪs/ US: /ˈdeɪtəbeɪs/	An organized collection of data from which relevant records can be identified and extracted.
derived unit	UK: /dɪˈraɪvd ˈjuːnɪt/ US: /dɪˈraɪvd ˈjuːnət/	A unit formed from products or powers of base units according to the defining relationship for a quantity.
dimensional analysis	UK: /daɪˌmenʃənəl əˈnælɪsɪs/ US: /daɪˌmenʃənəl əˈnæləsɪs/	The checking or development of relationships by comparing the dimensions or base-unit structure of their quantities.
discrete variable	UK: /dɪˈskriːt ˈveə.ri.ə.bəl/ US: /dɪˈskriːt ˈver.i.ə.bəl/	A variable that takes separate countable values rather than every value in an interval.
environmental issue	UK: /ɪnˌvaɪrənˈmentəl ˈɪʃuː/ US: /ɪnˌvaɪrənˈmentəl ˈɪʃuː/	A potential effect of an investigation on the natural or built environment that must be recognized and addressed.
estimation	UK: /ˌestɪˈmeɪʃən/ US: /ˌestəˈmeɪʃən/	The use of available information and justified assumptions to obtain a reasonable approximate value.
ethical issue	UK: /ˈeθɪkəl ˈɪʃuː/ US: /ˈeθɪkəl ˈɪʃuː/	A concern about responsible treatment of people, living systems, data or resources in an investigation.
experimental technique	UK: /ɪkˌsperɪˈmentəl tekˈniːk/ US: /ɪkˌsperəˈmentəl tekˈniːk/	A practical procedure used to make observations or measurements safely and with suitable precision.
fundamental unit	UK: /ˌfʌndəˈmentəl ˈjuːnɪt/ US: /ˌfʌndəˈmentəl ˈjuːnət/	An SI base unit from which derived units are formed according to relationships between physical quantities.
histogram	UK: /ˈhɪstəɡræm/ US: /ˈhɪstəɡræm/	A graph using adjacent bars to show the frequency distribution of numerical data grouped into intervals.
hypothesis	UK: /haɪˈpɒθəsɪs/ US: /haɪˈpɑːθəsɪs/	A testable proposed explanation or relationship that can be investigated using evidence.
image analysis	UK: /ˈɪmɪdʒ əˈnælɪsɪs/ US: /ˈɪmɪdʒ əˈnæləsɪs/	The extraction of quantitative or qualitative information from still images.
light intensity	UK: /laɪt ɪnˈtensɪti/ US: /laɪt ɪnˈtensəti/	The radiant power passing through unit area normal to the direction of propagation.
limitation	UK: /ˌlɪmɪˈteɪʃən/ US: /ˌlɪməˈteɪʃən/	A feature of an investigation that restricts the scope, certainty or generalizability of its conclusion.
maximum-gradient line	UK: /ˌmæksɪməm ˈɡreɪ.di.ənt laɪn/ US: /ˌmæksəməm ˈɡreɪ.di.ənt laɪn/	The steepest plausible straight line consistent with the uncertainty bars of the plotted data.
measuring apparatus	UK: /ˈmeʒərɪŋ ˌæpəˈreɪtəs/ US: /ˈmeʒərɪŋ ˌæpəˈrætəs/	Equipment used to measure a physical quantity.
methodological weakness	UK: /ˌmeθədəˈlɒdʒɪkəl ˈwiːknəs/ US: /ˌmeθədəˈlɑːdʒɪkəl ˈwiːknəs/	A defect in the design or execution of a method that can reduce the quality of the evidence or conclusion.
methodology	UK: /ˌmeθəˈdɒlədʒi/ US: /ˌmeθəˈdɑːlədʒi/	The justified overall design and sequence of procedures used to answer a research question.
minimum-gradient line	UK: /ˌmɪnɪməm ˈɡreɪ.di.ənt laɪn/ US: /ˌmɪnəməm ˈɡreɪ.di.ənt laɪn/	The least steep plausible straight line consistent with the uncertainty bars of the plotted data.
model	UK: /ˈmɒdəl/ US: /ˈmɑːdəl/	A simplified representation of a system used to describe, explain or predict its behaviour within stated assumptions and limits.
non-linear graph	UK: /ˌnɒn ˈlɪniə ɡrɑːf/ US: /ˌnɑːn ˈlɪniər ɡræf/	A graph in which the plotted relationship is not represented by a straight line on the chosen axes.
percentage change	UK: /pəˈsentɪdʒ tʃeɪndʒ/ US: /pərˈsentɪdʒ tʃeɪndʒ/	The change from an initial value divided by the magnitude of the initial value, multiplied by $100\%$.
pie chart	UK: /ˈpaɪ tʃɑːt/ US: /ˈpaɪ tʃɑːrt/	A circular chart divided into sectors whose angles or areas represent proportions of a whole.
pilot study	UK: /ˈpaɪlət ˌstʌdi/ US: /ˈpaɪlət ˌstʌdi/	A small preliminary trial used to test and refine an investigation’s methodology.
point of application	UK: /ˌpɔɪnt əv ˌæplɪˈkeɪʃən/ US: /ˌpɔɪnt əv ˌæpləˈkeɪʃən/	The position on a body at which a force is modelled as acting.
prediction	UK: /prɪˈdɪkʃən/ US: /prɪˈdɪkʃən/	A stated expected outcome derived from a hypothesis or scientific model.
processed data	UK: /ˈprəʊsest ˈdeɪtə/ US: /ˈprɑːsest ˈdeɪtə/	Data obtained after calculations, transformations or other analysis have been applied to raw data.
qualitative observation	UK: /ˈkwɒlɪtətɪv ˌɒbzəˈveɪʃən/ US: /ˈkwɑːləteɪtɪv ˌɑːbzərˈveɪʃən/	A non-numerical recorded description of a relevant property, event or change.
quantitative data	UK: /ˈkwɒntɪtətɪv ˈdeɪtə/ US: /ˈkwɑːntəteɪtɪv ˈdeɪtə/	Numerical observations or measurements recorded with appropriate units and uncertainties where applicable.
random error	UK: /ˈrændəm ˈerə/ US: /ˈrændəm ˈerər/	Unpredictable variation that causes repeated measurements to scatter on either side of a central value.
raw data	UK: /rɔː ˈdeɪtə/ US: /rɔː ˈdeɪtə/	Original observations or measurements recorded before calculation or transformation.
realistic improvement	UK: /ˌrɪəˈlɪstɪk ɪmˈpruːvmənt/ US: /ˌriːəˈlɪstɪk ɪmˈpruːvmənt/	A feasible, specific change to an investigation that addresses an identified weakness or limitation.
reliability	UK: /rɪˌlaɪəˈbɪləti/ US: /rɪˌlaɪəˈbɪləti/	The extent to which a method or measurement gives consistent results when repeated under the same conditions.
repeatability	UK: /rɪˌpiːtəˈbɪləti/ US: /rɪˌpiːtəˈbɪləti/	The closeness of results obtained by the same method, operator and apparatus over a short time under the same conditions.
reproducibility	UK: /rɪprəˌdjuːsəˈbɪləti/ US: /ˌriːprəˌduːsəˈbɪləti/	The closeness of results obtained when relevant conditions such as operator, apparatus or location are changed.
research question	UK: /rɪˈsɜːtʃ ˌkwestʃən/ US: /ˈriːsɝːtʃ ˌkwestʃən/	A focused, answerable question that defines what an investigation will examine.
safety issue	UK: /ˈseɪfti ˈɪʃuː/ US: /ˈseɪfti ˈɪʃuː/	A hazard or associated risk to people that must be identified and controlled in an investigation.
scale diagram	UK: /skeɪl ˈdaɪəɡræm/ US: /skeɪl ˈdaɪəɡræm/	A diagram in which lengths or vector magnitudes are drawn according to a stated scale.
scatter graph	UK: /ˈskætə ɡrɑːf/ US: /ˈskætər ɡræf/	A graph of paired numerical data used to show a possible relationship or correlation between two variables.
sensor	UK: /ˈsensə/ US: /ˈsensər/	A device that detects a physical quantity or change and produces a corresponding signal or data value.
SI prefix	UK: /ˌes ˈaɪ ˈpriːfɪks/ US: /ˌes ˈaɪ ˈpriːfɪks/	A standardized prefix attached to an SI unit to indicate a specified power-of-ten multiple or submultiple.
SI unit	UK: /ˌes ˈaɪ ˈjuːnɪt/ US: /ˌes ˈaɪ ˈjuːnət/	A unit of the International System of Units, including base units, derived units and their decimal multiples and submultiples formed with SI prefixes.
simulation	UK: /ˌsɪmjʊˈleɪʃən/ US: /ˌsɪmjəˈleɪʃən/	The use of a model, usually computational, to reproduce or predict aspects of a system’s behaviour.
sound intensity	UK: /saʊnd ɪnˈtensɪti/ US: /saʊnd ɪnˈtensəti/	The sound power passing through unit area normal to the direction of propagation.
spreadsheet	UK: /ˈspredʃiːt/ US: /ˈspredʃiːt/	Software that organizes data in cells and supports calculation, manipulation and graphical representation.
uncertainty bar	UK: /ʌnˈsɜːtənti bɑː/ US: /ʌnˈsɝːtənti bɑːr/	A graphical bar showing the stated uncertainty interval of a plotted value.
uncertainty propagation	UK: /ʌnˈsɜːtənti ˌprɒpəˈɡeɪʃən/ US: /ʌnˈsɝːtənti ˌprɑːpəˈɡeɪʃən/	The determination of uncertainty in a processed result from the uncertainties in the measured input quantities.
validity	UK: /vəˈlɪdəti/ US: /vəˈlɪdəti/	The extent to which an investigation’s design and evidence support the conclusion claimed for the research question.
video analysis	UK: /ˈvɪdiəʊ əˈnælɪsɪs/ US: /ˈvɪdioʊ əˈnæləsɪs/	The extraction of position, time or other data from successive frames of a video recording.

Mathematical terminology used in IB Physics

This section covers the mathematical terminology used in IB Physics for algebra, functions and graphs, geometry and trigonometry, vectors, calculus, statistics, data analysis and uncertainty. Some terms also appear earlier in specific physical contexts; here they are defined in their general mathematical sense.

Mathematical notation and operations

Term	Pronunciation	Definition
mathematical notation	UK: /ˌmæθəˈmætɪkəl nəʊˈteɪʃən/ US: /ˌmæθəˈmætɪkəl noʊˈteɪʃən/	A system of symbols and conventions used to represent mathematical quantities, operations and relations.
symbol	UK: /ˈsɪmbəl/ US: /ˈsɪmbəl/	A written sign used to represent a quantity, operation, relation or object.
equality	UK: /ɪˈkwɒləti/ US: /ɪˈkwɑːləti/	A statement that two mathematical expressions have the same value.
inequality	UK: /ˌɪnɪˈkwɒləti/ US: /ˌɪnɪˈkwɑːləti/	A statement comparing two expressions using relations such as greater than or less than.
plus sign	UK: /ˈplʌs saɪn/ US: /ˈplʌs saɪn/	The symbol $+$, used for addition or to indicate a positive value.
minus sign	UK: /ˈmaɪnəs saɪn/ US: /ˈmaɪnəs saɪn/	The symbol $-$, used for subtraction, a negative value or an opposite direction.
multiplication	UK: /ˌmʌltɪplɪˈkeɪʃən/ US: /ˌmʌltəpləˈkeɪʃən/	The operation of combining factors to obtain a product.
division	UK: /dɪˈvɪʒən/ US: /dɪˈvɪʒən/	The operation of forming the quotient of a dividend and a non-zero divisor.
sum	UK: /sʌm/ US: /sʌm/	The result of addition, or a quantity formed by adding terms.
difference	UK: /ˈdɪf.ər.əns/ US: /ˈdɪf.ɚ.əns/	The result obtained by subtracting one quantity from another.
product	UK: /ˈprɒdʌkt/ US: /ˈprɑːdʌkt/	The result of multiplication.
quotient	UK: /ˈkwəʊʃənt/ US: /ˈkwoʊʃənt/	The result of division.
absolute value	UK: /ˈæbsəluːt ˈvæljuː/ US: /ˈæbsəluːt ˈvæljuː/	The non-negative distance of a real number from zero, written $\lvert x\rvert$.
change in	UK: /ˈtʃeɪndʒ ɪn/ US: /ˈtʃeɪndʒ ɪn/	The final value minus the initial value, commonly represented by the symbol $\Delta$.
ratio	UK: /ˈreɪʃiəʊ/ US: /ˈreɪʃioʊ/	A comparison of two quantities by division.
fraction	UK: /ˈfrækʃən/ US: /ˈfrækʃən/	A number or algebraic expression written as one quantity divided by another non-zero quantity.
numerator	UK: /ˈnjuːməreɪtə/ US: /ˈnuːməreɪtər/	The quantity written above the fraction bar.
denominator	UK: /dɪˈnɒmɪneɪtə/ US: /dɪˈnɑːməneɪtər/	The non-zero quantity written below the fraction bar.
decimal	UK: /ˈdesɪməl/ US: /ˈdesəməl/	A representation of a number using powers of ten and a decimal point.
percentage	UK: /pəˈsentɪdʒ/ US: /pərˈsentɪdʒ/	A ratio expressed as a number of parts per hundred.
summation notation	UK: /səˈmeɪʃən nəʊˈteɪʃən/ US: /səˈmeɪʃən noʊˈteɪʃən/	Compact notation using the sigma symbol $\Sigma$ to represent the sum of a sequence of terms.
subscript	UK: /ˈsʌbskrɪpt/ US: /ˈsʌbskrɪpt/	A smaller symbol written below and to the right of another symbol, often used as a label or index.
superscript	UK: /ˈsuːpəskrɪpt/ US: /ˈsuːpərskrɪpt/	A smaller symbol written above and to the right of another symbol, often used as an exponent.

Algebra and proportionality

Term	Pronunciation	Definition
number	UK: /ˈnʌmbə/ US: /ˈnʌmbər/	A mathematical object used to count, measure or label quantities.
integer	UK: /ˈɪntɪdʒə/ US: /ˈɪntədʒər/	A member of the set $\{\ldots,-2,-1,0,1,2,\ldots\}$.
positive number	UK: /ˈpɒzɪtɪv ˈnʌmbə/ US: /ˈpɑːzətɪv ˈnʌmbər/	A real number greater than zero.
negative number	UK: /ˈneɡətɪv ˈnʌmbə/ US: /ˈneɡətɪv ˈnʌmbər/	A real number less than zero.
variable	UK: /ˈveə.ri.ə.bəl/ US: /ˈver.i.ə.bəl/	A symbol representing a quantity whose value may vary or be unknown.
constant	UK: /ˈkɒnstənt/ US: /ˈkɑːnstənt/	A quantity whose value is fixed within the context being considered.
coefficient	UK: /ˌkəʊɪˈfɪʃənt/ US: /ˌkoʊəˈfɪʃənt/	A numerical or algebraic factor multiplying a term.
term	UK: /tɜːm/ US: /tɝːm/	A single part of an expression separated from other parts by addition or subtraction.
expression	UK: /ɪkˈspreʃən/ US: /ɪkˈspreʃən/	A mathematical combination of numbers, variables and operations that does not assert an equality.
equation	UK: /ɪˈkweɪʒən/ US: /ɪˈkweɪʒən/	A statement that two mathematical expressions are equal.
formula	UK: /ˈfɔːmjələ/ US: /ˈfɔːrmjələ/	An equation expressing a general relationship between quantities.
identity	UK: /aɪˈdentɪti/ US: /aɪˈdentəti/	An equality that is true for every permitted value of its variables.
subject of a formula	UK: /ˈsʌbdʒɪkt əv ə ˈfɔːmjələ/ US: /ˈsʌbdʒɪkt əv ə ˈfɔːrmjələ/	The variable isolated on one side of a formula.
rearrangement	UK: /ˌriːəˈreɪndʒmənt/ US: /ˌriːəˈreɪndʒmənt/	An algebraic transformation that changes the form of an equation while preserving its solutions.
substitution	UK: /ˌsʌbstɪˈtjuːʃən/ US: /ˌsʌbstəˈtuːʃən/	The replacement of a symbol by a numerical value or an equivalent expression.
solution	UK: /səˈluːʃən/ US: /səˈluːʃən/	A value or set of values that satisfies an equation or system of equations.
simultaneous equations	UK: /ˌsɪməlˈteɪniəs ɪˈkweɪʒənz/ US: /ˌsaɪməlˈteɪniəs ɪˈkweɪʒənz/	Two or more equations whose common solution must satisfy all equations at the same time.
proportion	UK: /prəˈpɔːʃən/ US: /prəˈpɔːrʃən/	A statement that two ratios are equal.
directly proportional	UK: /daɪˈrektli prəˈpɔːʃənəl/ US: /dəˈrektli prəˈpɔːrʃənəl/	Related so that the ratio of the dependent quantity to the independent quantity is constant: $y=kx$.
inversely proportional	UK: /ɪnˈvɜːsli prəˈpɔːʃənəl/ US: /ɪnˈvɝːsli prəˈpɔːrʃənəl/	Related so that the product of the two quantities is constant: $y=k/x$.
exponent	UK: /ɪkˈspəʊnənt/ US: /ɪkˈspoʊnənt/	The number or expression indicating the power to which a base is raised.
power	UK: /paʊə/ US: /ˈpaʊ.ɚ/	An expression formed by raising a base to an exponent, such as $x^n$.
square	UK: /skweə/ US: /skwer/	The second power of a quantity: $x^2$.
square root	UK: /skweə ruːt/ US: /skwer ruːt/	A number that, when squared, gives the original number.
cube	UK: /kjuːb/ US: /kjuːb/	The third power of a quantity: $x^3$.
cube root	UK: /kjuːb ruːt/ US: /kjuːb ruːt/	A number that, when cubed, gives the original number.
reciprocal	UK: /rɪˈsɪprəkəl/ US: /rɪˈsɪprəkəl/	The multiplicative inverse of a non-zero number $x$, equal to $1/x$.
scientific notation	UK: /ˌsaɪənˈtɪfɪk nəʊˈteɪʃən/ US: /ˌsaɪənˈtɪfɪk noʊˈteɪʃən/	A representation of a number in the form $a\times10^n$, where $1\leq\lvert a\rvert<10$ and $n$ is an integer.
order of magnitude	UK: /ˌɔːdər əv ˈmæɡnɪtjuːd/ US: /ˌɔːrdər əv ˈmæɡnətuːd/	The power of ten that characterizes the approximate scale of a quantity.
logarithm	UK: /ˈlɒɡərɪðəm/ US: /ˈlɑːɡərɪðəm/	The exponent to which a specified base must be raised to obtain a given number.
natural logarithm	UK: /ˈnætʃ.ər.əl ˈlɒɡərɪðəm/ US: /ˈnætʃ.ɚ.əl ˈlɑːɡərɪðəm/	A logarithm with base $e$, written $\ln x$.
exponential function	UK: /ˌek.spəˈnen.ʃəl ˈfʌŋkʃən/ US: /ˌek.spoʊˈnen.ʃəl ˈfʌŋkʃən/	A function in which the variable occurs in the exponent, such as $y=Ae^{kx}$.

Functions and graphs

Term	Pronunciation	Definition
function	UK: /ˈfʌŋkʃən/ US: /ˈfʌŋkʃən/	A rule that assigns exactly one output value to each permitted input value.
independent variable	UK: /ˌɪndɪˈpendənt ˈveə.ri.ə.bəl/ US: /ˌɪndɪˈpendənt ˈver.i.ə.bəl/	The input or explanatory variable deliberately selected or changed to investigate its effect on another variable; it is normally plotted on the horizontal axis.
dependent variable	UK: /dɪˈpendənt ˈveə.ri.ə.bəl/ US: /dɪˈpendənt ˈver.i.ə.bəl/	The measured or calculated response variable whose value depends on the independent variable; it is normally plotted on the vertical axis.
coordinate	UK: /kəʊˈɔːdɪnət/ US: /koʊˈɔːrdənət/	A number, or one of a set of numbers, specifying the position of a point.
origin	UK: /ˈɒrɪdʒɪn/ US: /ˈɔːrədʒɪn/	The point at which the coordinate axes intersect and all coordinates are zero.
axis	UK: /ˈæk.sɪs/ US: /ˈæk.sɪs/	A reference line on a graph or coordinate system along which values are measured.
horizontal axis	UK: /ˌhɒrɪˈzɒntəl ˈæk.sɪs/ US: /ˌhɔːrəˈzɑːntəl ˈæk.sɪs/	The left-to-right axis of a graph, commonly used for the independent variable.
vertical axis	UK: /ˈvɜːtɪkəl ˈæk.sɪs/ US: /ˈvɝːtɪkəl ˈæk.sɪs/	The bottom-to-top axis of a graph, commonly used for the dependent variable.
axis scale	UK: /ˈæk.sɪs skeɪl/ US: /ˈæk.sɪs skeɪl/	The numerical spacing and range used to represent values along an axis.
graph	UK: /ɡrɑːf/ US: /ɡræf/	A visual representation of the relationship between variables.
plot	UK: /plɒt/ US: /plɑːt/	A graph or the act of marking data points on a graph.
data point	UK: /ˈdeɪtə pɔɪnt/ US: /ˈdeɪtə pɔɪnt/	A plotted point representing one pair or set of measured values.
curve	UK: /kɜːv/ US: /kɝːv/	A continuous line representing a relationship that need not be linear.
straight line	UK: /streɪt laɪn/ US: /streɪt laɪn/	A line with constant gradient.
linear relationship	UK: /ˈlɪniə rɪˈleɪʃənʃɪp/ US: /ˈlɪniər riˈleɪʃənʃɪp/	A relationship represented by a straight-line graph, generally written $y=mx+c$.
inverse-square relationship	UK: /ˌɪnvɜːs ˈskweə rɪˈleɪʃənʃɪp/ US: /ˌɪnvɝːs ˈskwer riˈleɪʃənʃɪp/	A relationship of the form $y=k/x^2$.
gradient	UK: /ˈɡreɪ.di.ənt/ US: /ˈɡreɪ.di.ənt/	The change in the vertical coordinate divided by the corresponding change in the horizontal coordinate.
intercept	UK: /ˈɪntəsept/ US: /ˈɪntərsept/	The coordinate at which a graph crosses an axis.
tangent to a curve	UK: /ˈtændʒənt tə ə kɜːv/ US: /ˈtændʒənt tə ə kɝːv/	A straight line that has the same local gradient as a curve at the point of contact.
secant line	UK: /ˈsiːkənt laɪn/ US: /ˈsiːkənt laɪn/	A straight line passing through two distinct points on a curve.
maximum	UK: /ˈmæksɪməm/ US: /ˈmæksəməm/	The greatest value of a quantity within a specified domain or interval.
minimum	UK: /ˈmɪnɪməm/ US: /ˈmɪnəməm/	The least value of a quantity within a specified domain or interval.
turning point	UK: /ˈtɜːnɪŋ pɔɪnt/ US: /ˈtɝːnɪŋ pɔɪnt/	A point at which a curve changes from increasing to decreasing or from decreasing to increasing.
asymptote	UK: /ˈæsɪmtəʊt/ US: /ˈæsɪmtoʊt/	A line that a curve approaches arbitrarily closely in a limiting region.
interpolation	UK: /ɪnˌtɜːpəˈleɪʃən/ US: /ɪnˌtɝːpəˈleɪʃən/	Estimation of a value within the range of measured data.
extrapolation	UK: /ɪkˌstræpəˈleɪʃən/ US: /ɪkˌstræpəˈleɪʃən/	Estimation of a value outside the range of measured data.
linearization	UK: /ˌlɪniəraɪˈzeɪʃən/ US: /ˌlɪniərəˈzeɪʃən/	A transformation of variables that converts a non-linear relationship into a linear one.
logarithmic scale	UK: /ˌlɒɡəˈrɪðmɪk skeɪl/ US: /ˌlɑːɡəˈrɪðmɪk skeɪl/	A scale on which equal distances represent equal ratios rather than equal differences.
best-fit line	UK: /ˌbest ˈfɪt laɪn/ US: /ˌbest ˈfɪt laɪn/	A line chosen to represent the overall trend of a set of data points.
residual	UK: /rɪˈzɪdjuəl/ US: /rɪˈzɪdʒuəl/	The observed value minus the value predicted by a fitted model.

Geometry and trigonometry

Term	Pronunciation	Definition
angle	UK: /ˈæŋɡəl/ US: /ˈæŋɡəl/	The amount of rotation between two intersecting lines or directions.
degree	UK: /dɪˈɡriː/ US: /dɪˈɡriː/	An angular unit equal to one three-hundred-and-sixtieth of a complete revolution.
radian	UK: /ˈreɪdiən/ US: /ˈreɪdiən/	The SI-derived angular unit; one radian subtends an arc whose length equals the radius.
arc	UK: /ɑːk/ US: /ɑːrk/	A portion of the circumference of a circle.
arc length	UK: /ɑːk leŋθ/ US: /ɑːrk leŋθ/	The distance measured along a circular arc, equal to $s=r\theta$ when $\theta$ is in radians.
circumference	UK: /səˈkʌmfərəns/ US: /sərˈkʌmfərəns/	The perimeter of a circle, equal to $2\pi r$.
radius	UK: /ˈreɪ.di.əs/ US: /ˈreɪ.di.əs/	The distance from the centre of a circle or sphere to its boundary.
diameter	UK: /daɪˈæm.iː.tə/ US: /daɪˈæm.iː.t̬ɚ/	A straight line through the centre of a circle or sphere joining two boundary points; its length is $2r$.
perimeter	UK: /pəˈrɪmɪtə/ US: /pəˈrɪmətər/	The total length of the boundary of a plane shape.
area	UK: /ˈeəriə/ US: /ˈeriə/	The measure of the extent of a two-dimensional region.
surface area	UK: /ˈsɜːfɪs ˈeəriə/ US: /ˈsɝːfəs ˈeriə/	The total area of the outer surface of a three-dimensional object.
cross-sectional area	UK: /ˌkrɒs ˈsekʃənəl ˈeəriə/ US: /ˌkrɔːs ˈsekʃənəl ˈeriə/	The area of a section formed by cutting an object with a plane.
volume	UK: /ˈvɒljuːm/ US: /ˈvɑːljuːm/	The measure of the three-dimensional space occupied by an object or region.
right-angled triangle	UK: /ˌraɪt æŋɡəld ˈtraɪæŋɡəl/ US: /ˌraɪt æŋɡəld ˈtraɪæŋɡəl/	A triangle containing one angle of $90^\circ$.
hypotenuse	UK: /haɪˈpɒtənjuːs/ US: /haɪˈpɑːtənuːs/	The side opposite the right angle in a right-angled triangle.
adjacent side	UK: /əˈdʒeɪsənt saɪd/ US: /əˈdʒeɪsənt saɪd/	Relative to a chosen acute angle, the non-hypotenuse side that touches that angle.
opposite side	UK: /ˈɒpəzɪt saɪd/ US: /ˈɑːpəzət saɪd/	Relative to a chosen angle, the side lying across from that angle.
sine	UK: /saɪn/ US: /saɪn/	For an acute angle in a right-angled triangle, the ratio of opposite side to hypotenuse.
cosine	UK: /ˈkəʊsaɪn/ US: /ˈkoʊsaɪn/	For an acute angle in a right-angled triangle, the ratio of adjacent side to hypotenuse.
tangent function	UK: /ˈtændʒənt ˈfʌŋkʃən/ US: /ˈtændʒənt ˈfʌŋkʃən/	The trigonometric function defined by $\tan\theta=\sin\theta/\cos\theta$; in a right-angled triangle it is opposite divided by adjacent.
inverse sine	UK: /ˌɪnvɜːs ˈsaɪn/ US: /ˌɪnvɝːs ˈsaɪn/	The inverse function of sine on a restricted domain, used to determine an angle from its sine.
inverse cosine	UK: /ˌɪnvɜːs ˈkəʊsaɪn/ US: /ˌɪnvɝːs ˈkoʊsaɪn/	The inverse function of cosine on a restricted domain, used to determine an angle from its cosine.
inverse tangent	UK: /ˌɪnvɜːs ˈtændʒənt/ US: /ˌɪnvɝːs ˈtændʒənt/	The inverse function of tangent on a restricted domain, used to determine an angle from its tangent.
Pythagorean theorem	UK: /paɪˌθæɡəˈriːən ˈθɪərəm/ US: /paɪˌθæɡəˈriːən ˈθɪrəm/	The theorem that $a^2+b^2=c^2$ for a right-angled triangle with hypotenuse $c$.
similar triangles	UK: /ˈsɪmɪlə ˈtraɪæŋɡəlz/ US: /ˈsɪmələr ˈtraɪæŋɡəlz/	Triangles with equal corresponding angles and proportional corresponding sides.
parallel	UK: /ˈpærəlel/ US: /ˈperəlel/	Describing coplanar lines that do not meet, planes with the same normal direction, or vectors that are scalar multiples of each other.
perpendicular	UK: /ˌpɜːpənˈdɪkjələ/ US: /ˌpɝːpənˈdɪkjələr/	Meeting or oriented at a right angle.
normal	UK: /ˈnɔːməl/ US: /ˈnɔːrməl/	A line or direction perpendicular to the tangent line of a curve or the tangent plane of a surface at a specified point.

Vectors

Term	Pronunciation	Definition
scalar	UK: /ˈskeɪlə/ US: /ˈskeɪlər/	A quantity specified by magnitude only.
vector	UK: /ˈvektə/ US: /ˈvektər/	A quantity specified by both magnitude and direction.
magnitude	UK: /ˈmæɡnɪtjuːd/ US: /ˈmæɡnətuːd/	The non-negative size or length of a vector.
direction	UK: /dəˈrekʃən/ US: /dəˈrekʃən/	The orientation in which a vector points.
component	UK: /kəmˈpəʊnənt/ US: /kəmˈpoʊnənt/	The projection of a vector along a chosen direction or axis.
horizontal component	UK: /ˌhɒrɪˈzɒntəl kəmˈpəʊnənt/ US: /ˌhɔːrəˈzɑːntəl kəmˈpoʊnənt/	The component of a vector along the horizontal axis.
vertical component	UK: /ˈvɜːtɪkəl kəmˈpəʊnənt/ US: /ˈvɝːtɪkəl kəmˈpoʊnənt/	The component of a vector along the vertical axis.
vector addition	UK: /ˈvektə əˈdɪʃən/ US: /ˈvektər əˈdɪʃən/	The operation of combining vectors to obtain their resultant.
vector subtraction	UK: /ˈvektə səbˈtrækʃən/ US: /ˈvektər səbˈtrækʃən/	The addition of the negative of one vector to another vector.
resultant vector	UK: /rɪˈzʌltənt ˈvektə/ US: /rɪˈzʌltənt ˈvektər/	The single vector equal to the vector sum of two or more vectors.
resolution of a vector	UK: /ˌrezəˈluːʃən əv ə ˈvektə/ US: /ˌrezəˈluːʃən əv ə ˈvektər/	The process of expressing a vector as components along chosen directions.
unit vector	UK: /ˈjuːnɪt ˈvektə/ US: /ˈjuːnət ˈvektər/	A vector of magnitude one used to specify a direction.
scalar product	UK: /ˈskeɪlə ˈprɒdʌkt/ US: /ˈskeɪlər ˈprɑːdʌkt/	The scalar operation $\boldsymbol{a}\cdot\boldsymbol{b}=ab\cos\theta$.
vector diagram	UK: /ˈvektə ˈdaɪəɡræm/ US: /ˈvektər ˈdaɪəɡræm/	A diagram in which directed line segments represent vectors to scale or schematically.
head-to-tail method	UK: /ˌhed tə ˈteɪl ˈmeθəd/ US: /ˌhed tə ˈteɪl ˈmeθəd/	A graphical method of vector addition in which the tail of each vector is placed at the head of the preceding vector.
parallelogram method	UK: /ˌpærəˈleləɡræm ˈmeθəd/ US: /ˌpærəˈleləɡræm ˈmeθəd/	A graphical method in which two vectors form adjacent sides of a parallelogram and the diagonal gives the resultant.

Calculus

Term	Pronunciation	Definition
limit	UK: /ˈlɪmɪt/ US: /ˈlɪmɪt/	The value that a function or sequence approaches as its input approaches a specified value.
derivative	UK: /dɪˈrɪvətɪv/ US: /dɪˈrɪvətɪv/	The instantaneous rate of change of a function with respect to its variable.
differentiation	UK: /ˌdɪfərenʃiˈeɪʃən/ US: /ˌdɪfərenʃiˈeɪʃən/	The process of finding a derivative.
rate of change	UK: /reɪt əv tʃeɪndʒ/ US: /reɪt əv tʃeɪndʒ/	The change in a dependent quantity divided by the corresponding change in an independent quantity over a specified interval.
instantaneous rate of change	UK: /ˌɪnstənˈteɪniəs reɪt əv tʃeɪndʒ/ US: /ˌɪnstənˈtæniəs reɪt əv tʃeɪndʒ/	The limiting rate of change at one point, represented by a derivative.
differential	UK: /ˌdɪfəˈrenʃəl/ US: /ˌdɪfəˈrenʃəl/	In notation such as $\mathrm{d}x$, the symbol identifies the variable of differentiation or integration and may represent a differential change.
finite difference	UK: /ˌfaɪnaɪt ˈdɪf.ər.əns/ US: /ˌfaɪnaɪt ˈdɪf.ɚ.əns/	A difference such as $\Delta x$ between two distinct finite values.
integral	UK: /ˈɪntɪɡrəl/ US: /ˈɪntəɡrəl/	A mathematical quantity representing accumulation; a definite integral gives a signed accumulated total over an interval.
integration	UK: /ˌɪntɪˈɡreɪʃən/ US: /ˌɪntəˈɡreɪʃən/	The process of evaluating an integral.
definite integral	UK: /ˌdefɪnət ˈɪntɪɡrəl/ US: /ˌdefɪnət ˈɪntəɡrəl/	An integral evaluated between specified lower and upper limits.
area under a curve	UK: /ˈeəriə ˌʌndər ə kɜːv/ US: /ˈeriə ˌʌndər ə kɝːv/	The signed area between a graph and its horizontal axis over a specified interval, represented by a definite integral.

Statistics, data and uncertainty

Term	Pronunciation	Definition
data	UK: /ˈdeɪtə/ US: /ˈdeɪtə/	Recorded observations or measurements used for analysis.
data set	UK: /ˈdeɪtə set/ US: /ˈdeɪtə set/	A collection of related data values.
sample	UK: /ˈsɑːmpəl/ US: /ˈsæmpəl/	A subset of observations selected from a larger population.
population	UK: /ˌpɒpjəˈleɪʃən/ US: /ˌpɑːpjəˈleɪʃən/	The complete set of objects, events or measurements about which an inference is made.
probability	UK: /ˌprɒbəˈbɪləti/ US: /ˌprɑːbəˈbɪləti/	A number from zero to one that quantifies the likelihood of an event.
distribution	UK: /ˌdɪs.trɪˈbjuː.ʃən/ US: /ˌdɪs.trɪˈbjuː.ʃən/	A description of how data values or probabilities are spread over possible outcomes.
normal distribution	UK: /ˌnɔːməl ˌdɪs.trɪˈbjuː.ʃən/ US: /ˌnɔːrməl ˌdɪs.trɪˈbjuː.ʃən/	A symmetric bell-shaped probability distribution determined by its mean and standard deviation.
mean	UK: /miːn/ US: /miːn/	The arithmetic average, found by dividing the sum of values by the number of values.
arithmetic mean	UK: /ˌærɪθˈmetɪk miːn/ US: /ˌerɪθˈmetɪk miːn/	The sum of all values divided by the number of values.
median	UK: /ˈmiːdiən/ US: /ˈmiːdiən/	The middle value of an ordered data set, or the mean of the two middle values when the number of values is even.
mode	UK: /məʊd/ US: /moʊd/	The value occurring most frequently in a data set.
range	UK: /reɪndʒ/ US: /reɪndʒ/	The maximum value minus the minimum value in a data set.
variance	UK: /ˈveəriəns/ US: /ˈveriəns/	The mean squared deviation of values from their mean, with the precise divisor depending on whether a population or sample variance is used.
standard deviation	UK: /ˌstændəd ˌdiːviˈeɪʃən/ US: /ˌstændərd ˌdiːviˈeɪʃən/	The square root of the variance, measuring the spread of data around the mean.
uncertainty	UK: /ʌnˈsɜːtənti/ US: /ʌnˈsɝːtənti/	A quantified estimate of the interval within which the true value of a measured quantity is reasonably expected to lie.
absolute uncertainty	UK: /ˈæbsəluːt ʌnˈsɜːtənti/ US: /ˈæbsəluːt ʌnˈsɝːtənti/	An uncertainty expressed in the same units as the measured quantity.
fractional uncertainty	UK: /ˈfrækʃənəl ʌnˈsɜːtənti/ US: /ˈfrækʃənəl ʌnˈsɝːtənti/	The absolute uncertainty divided by the magnitude of the measured value.
percentage uncertainty	UK: /pəˈsentɪdʒ ʌnˈsɜːtənti/ US: /pərˈsentɪdʒ ʌnˈsɝːtənti/	The fractional uncertainty multiplied by $100\%$.
random uncertainty	UK: /ˈrændəm ʌnˈsɜːtənti/ US: /ˈrændəm ʌnˈsɝːtənti/	Uncertainty associated with unpredictable variations that cause repeated measurements to scatter.
systematic error	UK: /ˌsɪstəˈmætɪk ˈerə/ US: /ˌsɪstəˈmætɪk ˈerər/	A repeatable or predictable bias in a measurement method that is not reduced by taking more repeated measurements under unchanged conditions.
accuracy	UK: /ˈækjərəsi/ US: /ˈækjərəsi/	The degree of agreement between a measured result and an accepted or reference value.
precision	UK: /prɪˈsɪʒən/ US: /prɪˈsɪʒən/	The degree of agreement among repeated measurements made under the same conditions.
significant figures	UK: /sɪɡˌnɪfɪkənt ˈfɪɡəz/ US: /sɪɡˌnɪfɪkənt ˈfɪɡjərz/	The meaningful digits retained in a measured or calculated value at a level appropriate to its uncertainty and the input data.
decimal places	UK: /ˈdesɪməl ˈpleɪsɪz/ US: /ˈdesəməl ˈpleɪsɪz/	The number of digits written to the right of the decimal point.
error bar	UK: /ˈerə bɑː/ US: /ˈerər bɑːr/	A graphical line showing the uncertainty interval associated with a plotted value.
upper bound	UK: /ˈʌpə baʊnd/ US: /ˈʌpər baʊnd/	The greatest value permitted by a stated interval or uncertainty.
lower bound	UK: /ˈləʊə baʊnd/ US: /ˈloʊər baʊnd/	The least value permitted by a stated interval or uncertainty.
percentage difference	UK: /pəˈsentɪdʒ ˈdɪf.ər.əns/ US: /pərˈsentɪdʒ ˈdɪf.ɚ.əns/	The absolute difference between two experimental values divided by their mean, multiplied by $100\%$.
percentage error	UK: /pəˈsentɪdʒ ˈerə/ US: /pərˈsentɪdʒ ˈerər/	The absolute difference between an experimental value and an accepted value divided by the magnitude of the accepted value, multiplied by $100\%$.
correlation	UK: /ˌkɒrəˈleɪʃən/ US: /ˌkɔːrəˈleɪʃən/	A statistical association between two variables; correlation alone does not establish causation.
positive correlation	UK: /ˈpɒzɪtɪv ˌkɒrəˈleɪʃən/ US: /ˈpɑːzətɪv ˌkɔːrəˈleɪʃən/	A relationship in which larger values of one variable tend to be associated with larger values of another.
negative correlation	UK: /ˈneɡətɪv ˌkɒrəˈleɪʃən/ US: /ˈneɡətɪv ˌkɔːrəˈleɪʃən/	A relationship in which larger values of one variable tend to be associated with smaller values of another.
linear regression	UK: /ˈlɪniə rɪˈɡreʃən/ US: /ˈlɪniər rɪˈɡreʃən/	A statistical method for fitting a straight-line model to data.
uncertainty in the gradient	UK: /ʌnˈsɜːtənti ɪn ðə ˈɡreɪ.di.ənt/ US: /ʌnˈsɝːtənti ɪn ðə ˈɡreɪ.di.ənt/	An estimate of the range of plausible gradient values consistent with the data and their uncertainties.
uncertainty in the intercept	UK: /ʌnˈsɜːtənti ɪn ði ˈɪntəsept/ US: /ʌnˈsɝːtənti ɪn ði ˈɪntərsept/	An estimate of the range of plausible intercept values consistent with the data and their uncertainties.
outlier	UK: /ˈaʊtlaɪə/ US: /ˈaʊtlaɪər/	A data value lying unusually far from the general pattern of the remaining data.

References

1. International Baccalaureate Organization, Physics guide, first assessment 2025, updated November 2024.
2. International Baccalaureate Organization, Physics data booklet, first assessment 2025, version 1.2.
3. Cambridge University Press, Cambridge English Dictionary and Cambridge English Pronouncing Dictionary.
4. Oxford University Press, Oxford Learner’s Dictionaries and Oxford pronunciation resources.
5. Carnegie Mellon University, CMU Pronouncing Dictionary.
6. Open Speech and Language Resources, BEEP Dictionary; Britfone British English pronunciation lexicon.

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