French régime, from Old French regimen, regime, from Late Latin regimin-, regimen
- Date: 1776
- 1 a : regimen
- b : a regular pattern of occurrence or action (as of seasonal rainfall)
- c : the characteristic behavior or orderly procedure of a natural phenomenon or process
- 2 a : mode of rule or management
The word regime (occasionally spelled "régime") refers to a set of conditions, most often of a political nature. It may also be used synonymously with regimen, for example in the phrases "exercise regime" or "medical regime".
In politics, a regime is the form of government: the set of rules, cultural or social norms, etc. that regulate the operation of government and its interactions with society. For instance, the United States has one of the oldest regimes still active in the world, dating to the ratification of its Constitution in 1789. Although modern usage often gives the term a negative connotation, like an authoritarian one, Webster's definition clearly states that the word "regime" refers simply to a form of government.
The term is also used to distinguish what is actually being enforced from what is considered legitimate. Enforcement of an unconstitutional statute would be a regime but not a law.
In scientific discussions, a regime is a class of physical conditions defined by specific measures, where a particular physical phenomenon or boundary condition is significant. Very often a regime corresponds to a limiting condition. The region of measurable parameter space that corresponds to a regime is very often loosely defined. Examples include "the superfluid regime","the steady state regime", or "the femtosecond regime".
In geography and hydrography, "regime" refers to the changing conditions of river beds and other features, such as systems of sandbars.