Key terms & definitions

An ion made from two or more atoms joined together that acts as one charged unit, such as $\mathrm{NO_3^-}$.

A charged group of covalently bonded atoms, such as the nitrate ion, $\mathrm{NO_3^-}$.

A measurement formed from two or more quantities, such as distance divided by time.

A measure combining two quantities, such as distance divided by time, expressed in units such as mm/min.

A measure formed by combining two or more other measures, usually by division; examples include speed, density and pressure.

A sentence containing two or more main clauses joined together.

A shape formed by joining two or more simpler shapes.

A transmission with successive stages, including two components fixed to an intermediate shaft so that they rotate together.

A unit formed from more than one unit, usually by multiplication or division, such as $\text{g/dm}^3$ or $\text{m/s}$.

A unit formed by combining two or more units, usually by multiplication or division, such as metres per second.

A unit formed by combining units, such as metres per second (m/s).

A unit formed by combining two or more standard units, usually to describe one quantity per unit of another.

A secondary school admitting pupils of different abilities without selecting its intake through an academic entrance examination.

A secondary school that admits pupils across the ability range rather than selecting its intake by academic ability.

To force a substance into a smaller volume.

The property of a substance that allows its volume to decrease when pressure is applied.

A reduction in the volume occupied by a gas as an external force pushes its boundary inwards.

A region of a longitudinal wave where the particles of the medium are closer together than usual.

The process of reducing the size of a file so that it requires less storage space.

Wrapping an injured area with a supportive elastic bandage to help limit swelling.

A pushing action that tends to squash or shorten a material.

A manufacturing process in which polymer placed in a heated mould cavity is compressed by a closing plug using a hydraulic press.

A material's ability to withstand a pushing force without being crushed or deformed.

The maximum compressive force per unit area that a material can withstand before failing.

Resistance to being crushed by a compressive force.

Forcing someone to act or accept something against their will.

Required by law rather than left entirely to individual choice.

A legal order enabling a public authority to acquire property without the owner's agreement, with compensation.

Government provision of free school places for children within the compulsory education age range. In England, children aged 5–16 are entitled to a free state-school place; compulsory education does not mean that every child must attend a school.

A system in which eligible citizens are legally required to participate in voting, usually with a penalty for unjustified non-participation.