detention vs detain

detention is a noun but detain is not a noun.

Word	Noun	Adjective	Verb	Adverb
detention	Yes	No	No	No
detain	No	No	Yes	No

detention (noun)	detain (noun)
a punishment in which a student must stay at school after others have gone home
a state of being confined (usually for a short time)

detention (verb)	detain (verb)
	cause to be slowed down or delayed
	stop or halt
	deprive of freedom; take into confinement