Prisons are also known as penitentiaries, prisons, prisons, prisons (in American English), prisons (in American English), detention centers (in American English) or remand centers, which refer to facilities under state power where prisoners are forcibly restricted and deprived of various freedoms. Prison is the most commonly used prison in the criminal justice system: the person charged with a crime may be imprisoned until he is tried; if he pleads guilty or is convicted in a trial, he may be sentenced to a specific term of imprisonment. In addition to punishing crimes, prisons and prisons are often used by authoritarian regimes to deal with prisons that are considered opponents.

In American English, prison and prison are usually regarded as having separate definitions. Terms used in prisons or prison management often describe institutions where long-term detainees (for example, many years) are run by the state or federal government. The term prison tends to describe institutions that limit people to a shorter period of time (for example, shorter terms of sentence or pre-trial detention), usually run by local governments. Outside North America, prison and prison have the same meaning.

Prisons can be used as tools of political repression to punish what is considered to be a political crime, often without trial or other legitimate due process; such use is illegal under most forms of international law on just justice. During wartime, prisoners of war or detainees may be detained in military prisons or POW camps, and large numbers of civilians may be held in detention facilities.