Key terms & definitions

The percentage of output judged unsuitable for sale because it does not meet the required standards.

A return to addictive behaviour after a period of improvement or abstinence.

Units that measure compatible types of quantity and can therefore be converted between one another, such as metres and centimetres.

A database that organises data into related tables, using keys to link their records.

An operator that compares two values and produces a Boolean result, either True or False.

The proportion of a sample made up of a particular isotope, often expressed as a percentage.

The mean mass of the atoms of an element compared with one-twelfth of the mass of a carbon-12 atom; its symbol is $A_r$.

The weighted mean mass of an element’s atoms compared with one-twelfth of the mass of a carbon-12 atom. It has no unit.

The weighted mean mass of an atom of an element relative to one-twelfth of the mass of a carbon-12 atom; it takes account of the relative abundances of the element’s isotopes.

The average mass of an atom of an element compared with one-twelfth of the mass of a carbon-12 atom. It has no units.

The charge of a particle expressed by comparison with the magnitude of the charge on a proton.

A comparison of electric charge using proton charge as +1 and electron charge as −1.

The electrical charge of a particle compared with the magnitude of a proton’s charge, including a sign to show whether it is positive or negative.

Dating that establishes whether an object is older or younger than another, rather than giving its age in years.

Dating that establishes whether something is earlier or later than something else, without necessarily assigning calendar years.

Lacking the resources needed to obtain the diets, living conditions and participation in activities customary or widely accepted in one’s society.

The electric charge of a particle compared with the magnitude of the charge on a proton; a proton is assigned a relative charge of +1.

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

The sum of the relative atomic masses of all the atoms shown in a chemical formula. It has no unit.

The sum of the relative atomic masses of all the atoms shown in a chemical formula.

The sum of the relative atomic masses of all the atoms shown in a chemical formula. It has no units.

The proportion of trials in which an event occurred: $\frac{\text{number of occurrences}}{\text{total number of trials}}$.

The proportion of trials in which an outcome actually occurs: its frequency divided by the total number of trials.

The proportion of trials in which an event occurs: $\text{relative frequency}=\frac{\text{frequency of the event}}{\text{total number of trials}}$.

A poverty threshold set in relation to other households’ incomes. Townsend used income below 50% of the mean for the same household type.

A poverty measure that identifies households whose income falls below a chosen level relative to the income of comparable households.

A mass stated by comparison with an agreed reference rather than in kilograms.

The mass of a particle compared with a chosen reference mass; at GCSE, the proton is assigned a relative mass of 1.

A comparison of particle masses on a common scale. A proton and a neutron each have a relative mass of 1; an electron’s relative mass is very small.

The mass of a molecule compared with one-twelfth of the mass of a carbon-12 atom; it is found by adding the relative atomic masses of all the atoms in the formula.