Continuum

fr. Null-A Continuum by John C. Wright

Continuum theories or models explain variation as involving a gradual quantitative transition without abrupt changes or discontinuities. It can be contrasted with 'categorical' models which propose qualitatively different states.

In physics

In physics, for example, the space-time continuum model explains space and time as part of the same continuum rather than as separate entities. A spectrum in physics (e.g. of light) is often termed either a 'continuous spectrum' (energy at all wavelengths) or 'discrete spectrum' (energy at only certain wavelengths).

In contrast, the quantum theory includes quanta, which are distinguished from continuous amounts.

In psychology

In psychology, theories of mental phenomena can propose discrete differences between individuals (e.g. everyone has certain personality traits and not others) or a continuum (e.g. everyone lies somewhere on a particular personality dimension). This can also apply to fields such as law or sociology or ethics in explaining or judging variation in human behavior.

In psychiatry, categorical models seek to distinguish and define particular mental disorders or illnesses, whilst continuum or dimensional models propose that some people are more extreme than others on particular dimensions.