Key terms & definitions

The sum of the relative atomic masses of all the atoms in a molecule. Relative molecular mass, $M_r$, has no unit.

The sum of the relative atomic masses of all the atoms represented in a molecular formula.

The view that whether an action is right or wrong can depend on the circumstances.

An attitude that strongly opposes violence but allows that it might be justified in exceptional circumstances to prevent greater harm.

The relative mass of the particle being counted, found from the relative atomic masses of the atoms in its formula. It has no unit.

A mass compared with a standard based on carbon-12, with no unit. Use relative atomic mass for atoms and relative molecular or formula mass for molecules or formula units.

Poverty assessed in relation to the living standards of the society in which a person lives.

Poverty defined in relation to the living standards customary or widely accepted in a particular society.

A measure calculated as $1/t$ when different trials all reach the same fixed end point.

A value calculated as 1 divided by the time taken to reach the same endpoint in each trial; it is proportional to the reaction rate.

The ratio of the absolute risk in one group to the absolute risk in a comparison group: $\text{relative risk of A compared with B}=\frac{p_A}{p_B}$.

A rise in the sea’s average level compared with the land. It can result from rising ocean levels, sinking land, or both.

A comparison of the sizes of two objects, normally made after expressing both measurements in the same unit.

A monocular depth cue in which the smaller-looking of two objects of the same or similar actual size is perceived as further away.

A value that compares a particle's charge or mass with an agreed reference value rather than giving its absolute measurement.

The pressure of water demand on available renewable water supply, commonly measured as the ratio of demand to supply.

An electrically operated switch whose energised coil creates a magnetic field that moves an armature and changes the contacts in another circuit.

A neuron within the central nervous system that connects other neurons, including sensory and motor neurons.

A nerve cell in the central nervous system that passes impulses between sensory and motor neurones.

A neurone within the central nervous system that connects sensory and motor neurones.

Providing information previously kept from spectators, changing their understanding of events.

The extent to which data is suitable for the question being investigated, including the population, variables and time period.

How far information in a source can be trusted as an accurate account of what it describes.

The consistency of results when a method is repeated under comparable conditions.

The ability of an energy resource to provide energy when it is needed.

The extent to which an energy resource can provide a predictable supply when needed.

The ability of a product or service to perform as expected without failures.

A program’s ability to work consistently as intended without failing.

The extent to which findings can be trusted, taking account of the sample, data quality and variation.

The consistency of results when a test is repeated under the same conditions.