imprisonment vs custody

imprisonment and custody both are nouns.

Word	Noun	Adjective	Verb	Adverb
imprisonment	Yes	No	No	No
custody	Yes	No	No	No

As nouns, custody is a hyponym of imprisonment; that is, custody is a word with a more specific, narrower meaning than imprisonment:

imprisonment: the act of confining someone in a prison (or as if in a prison)
custody: holding by the police

Other hyponyms of imprisonment include lockdown, false imprisonment.

imprisonment (noun)	custody (noun)
the act of confining someone in a prison (or as if in a prison)	holding by the police
putting someone in prison or in jail as lawful punishment	(with `in') guardianship over; in divorce cases it is the right to house and care for and discipline a child
the state of being imprisoned	a state of being confined (usually for a short time)