Imprisonment (from imprison Old French, French emprisonner, from en in + prison prison, from Latin prensio, arrest, from prehendere, prendere, to seize) is the restraint of a person's liberty, for any cause whatsoever, whether by authority of the government, or by a person acting without such authority. In the latter case it is "false imprisonment". Imprisonment does not necessarily imply a place of confinement, with bolts and bars, but may be exercised by any use or display of force, lawfully or unlawfully, wherever displayed, even in the open street. People become prisoners, wherever they may be, by the mere word or touch of a duly authorized officer directed to that end. Usually, however, imprisonment is understood to imply an actual confinement in a jail or prison employed for the purpose according to the provisions of law.
England and Wales
In English law, imprisonment is the restraint of a person's liberty. The book Termes de la Ley contains the following definition:
Imprisonment is no other thing than the restraint of a man's liberty, whether it be in the open field, or in the stocks, or in the cage in the streets or in a man's own house, as well as in the common gaols; and in all the places the party so restrained is said to be a prisoner so long as he hath not his liberty freely to go at all times to all places whither he will without bail or mainprise or otherwise.
This passage was approved by Atkin and Duke LJJ in Meering v Grahame White Aviation Co. It is not imprisonment to prevent a person from proceeding along a particular way if it is possible for him to reach his intended destination by another route. Imprisonment without lawful cause is a tort called false imprisonment. Imprisonment is a type of sentence.