detainment vs custody

detainment and custody both are nouns.

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

As nouns, detainment and custody are synonyms defined as:

detainment and custody: a state of being confined (usually for a short time)

Other synonyms of detainment include detention, hold.

detainment (noun)	custody (noun)
a state of being confined (usually for a short time)	holding by the police
	(with `in') guardianship over; in divorce cases it is the right to house and care for and discipline a child
	a state of being confined (usually for a short time)