Cambridge IGCSE Physics 0625 Vocabulary Review (2026-2028)

Comprehensive vocabulary list of core and supplement physics terms and definitions as defined in the Cambridge IGCSE Physics 0625 syllabus for examinations in 2026-2028.

Speed

Distance travelled per unit time; defined by the equation $v = \frac{s}{t}$.

Velocity

The speed of an object in a given direction.

Acceleration

Change in velocity per unit time; defined by the equation $a = \frac{\Delta v}{\Delta t}$.

Acceleration of free fall ($g$)

Approximately constant for an object near the surface of the Earth, valued at approximately $9.8\,m/s^2$.

Mass

A measure of the quantity of matter in an object at rest relative to the observer.

Weight

A gravitational force on an object that has mass.

Gravitational field strength ($g$)

Force per unit mass; calculated as $g = \frac{W}{m}$.

Scalar quantity

A quantity that has magnitude (size) only, such as distance, speed, time, mass, energy, and temperature.

Vector quantity

A quantity that has both magnitude and direction, such as force, weight, velocity, acceleration, momentum, electric field strength, and gravitational field strength.

Density

Mass per unit volume; defined by the equation $\rho = \frac{m}{V}$.

Spring constant ($k$)

Force per unit extension; defined by the equation $k = \frac{F}{x}$.

Limit of proportionality

The point on a load–extension graph beyond which the extension is no longer proportional to the load.

Solid friction

The force between two surfaces that may impede motion and produce heating.

Moment of a force

A measure of the turning effect of a force, defined as $\text{moment} = \text{force} \times \text{perpendicular distance from the pivot}$.

Equilibrium

An object state where there is no resultant force and no resultant moment.

Centre of gravity

The point through which the whole weight of an object acts.

Momentum

The product of mass and velocity ($p = mv$).

Impulse

The product of force and the time for which the force acts ($\text{impulse} = F\Delta t = \Delta(mv)$).

Work done ($W$)

Mechanical or electrical energy transferred, defined by the equation $W = Fd = \Delta E$.

Efficiency

The ratio of useful energy output to total energy input, or useful power output to total power input, expressed as a percentage.

Power ($P$)

Work done per unit time or energy transferred per unit time ($P = \frac{W}{t}$ or $P = \frac{\Delta E}{t}$).

Pressure ($p$)

Force per unit area; defined by the equation $p = \frac{F}{A}$.

Absolute zero

The lowest possible temperature ($-273^\circ\text{C}$), where particles have the least kinetic energy.

Brownian motion

The random motion of microscopic particles in a suspension caused by random collisions with the particles of the gas or liquid.

Specific heat capacity

The energy required per unit mass per unit temperature increase ($c = \frac{\Delta E}{m\Delta\theta}$).

Evaporation

The escape of more-energetic particles from the surface of a liquid, which causes the cooling of the liquid.

Convection

Thermal energy transfer in liquids and gases caused by density changes.

Transverse wave

A wave where the direction of vibration is at right angles to the direction of propagation (e.g., electromagnetic radiation).

Longitudinal wave

A wave where the direction of vibration is parallel to the direction of propagation (e.g., sound waves).

Monochromatic light

Visible light of a single frequency.

Critical angle

The angle of incidence beyond which total internal reflection occurs.

Ultrasound

Sound with a frequency higher than $20\,\text{kHz}$.

Induced magnetism

Magnetism created in a magnetic material when it is placed in a magnetic field.

Electric field

A region in which an electric charge experiences a force.

Electric current ($I$)

The charge passing a point per unit time; defined as $I = \frac{Q}{t}$.

Electromotive force (e.m.f.)

The electrical work done by a source in moving a unit charge around a complete circuit.

Potential difference (p.d.)

The work done by a unit charge passing through a component.

Proton number ($Z$)

The number of protons in the nucleus of an atom; also known as the atomic number.

Nucleon number ($A$)

The total number of protons and neutrons in the nucleus of an atom; also known as the mass number.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Half-life

The time taken for half the nuclei of a particular isotope in any sample to decay.

Background radiation

Ionising radiation present in the environment from sources such as radon gas, rocks, food, and cosmic rays.

Light-year

The distance travelled in the vacuum of space by light in one year, equal to $9.5 \times 10^{15}\,m$.

Redshift

An increase in the observed wavelength of electromagnetic radiation emitted from receding stars and galaxies; evidence for the expanding Universe.

Hubble constant ($H_0$)

The ratio of the speed at which a galaxy is moving away from the Earth to its distance from the Earth; current estimate is $2.2 \times 10^{-18}\,\text{per second}$.

Accuracy

How close a measurement result is to the true value.

Precision

How close the measured values of a quantity are to each other.

Independent variable

The variable that is changed in a scientific experiment by the scientist.

Dependent variable

The variable that is observed or measured in a scientific experiment, which may change based on the independent variable.

Anomaly

A value in a set of results that appears to be outside the general pattern of the results.