Key terms & definitions

A row of soldiers standing side by side within a formation.

A person’s position within a social hierarchy, influenced by birth, family connections and titles; it is not identical to wealth.

The position of a value when a set of values is put in order.

The difference between the two ranks belonging to one pair of values, usually written $d$.

A test in which samples are placed in order according to a specified sensory property.

Money or valuables demanded or offered in exchange for releasing a prisoner.

A payment offered to secure the release of a captive or the return of a body.

A payment made to secure someone’s release. In Mark 10:45, Jesus describes giving his life as ‘a ransom for many’, presenting his death as a sacrifice that brings freedom to others.

Cortés’s seizure and holding of the Aztec ruler Montezuma as security against attack. During his captivity, Montezuma acknowledged King Charles’s authority and handed treasure to the Spanish.

Malware that can encrypt files so they cannot be used, then demand payment to unlock them.

Able to produce a result quickly.

A trusting, comfortable relationship between a researcher and a participant that can encourage cooperation and open discussion.

The improvement of relations between countries after a period of hostility.

A group of metallic elements used in electronic products, including in magnets and batteries. The abbreviation is REEs.

A region of a longitudinal wave where the particles of the medium are further apart than usual.

A region of a longitudinal wave where the particles of the medium are further apart than usual.

A hand tool with projecting teeth that cut away wood, particularly useful for shaping curves and irregular forms.

An Arabic term meaning messenger; used in this topic for a prophet entrusted with revealed scripture.

The quantity moving, or the amount of change occurring, per unit of time.

The change in a measured quantity divided by the time taken for that change.

How much a quantity changes per unit time.

A quantity expressed per unit of another quantity, such as metres travelled per second.

A comparison describing how much of one quantity there is per unit of another quantity, such as £12 per hour.

A measure expressing one quantity relative to another, such as the number of deaths during a year per 1,000 people.

A value expressed relative to a defined amount, such as the number of recorded offences per 100 matches.

The volume of blood passing a point per unit time.

The change in a quantity over a specified time interval, often expressed per year or per decade.

Change in a quantity divided by the time taken for that change.

The change in a quantity divided by the time taken for that change.

How much one quantity changes for each unit change in another quantity.