Other forms: detentions
Detention is being kept somewhere you would rather not be. At school it is the half hour after the bell, sitting in a classroom copying out lines while everyone else walks home; in the news it is a person held by the police or by immigration officers.
The two uses feel far apart, but the idea is one: somebody is held. School detention is countable — you get a detention, you have three detentions this term. The legal one is not: detention without trial, held in detention, a detention centre. The verb behind it is detain, and detain keeps a mild side that detention lost completely — sorry to detain you. Detention is never a small delay; it is a punishment or a confinement.
1noundetentionThe punishment of being made to stay at school after lessons have ended.
“He got a detention for arriving late three days running.”
2nounholdingThe holding of someone in official custody, or the state of being held.
“The journalist spent six weeks in detention.”
detention is a form of confinement.
Detention arrived through Middle French detention from Latin detentio. Underneath, it is nothing more than detain with -tion bolted on, which turns the act of holding somebody back into a thing that can be handed to you. That is why the school version and the police version are one word: in both, a person is being kept.
Latin
detentio
Middle French
détention
English, today
detention
Borrowed from Middle French détention, from Latin detentio. Equivalent to detain + tion.
Etymology from Wiktionary, CC BY-SA