penalty vs imprisonment

penalty and imprisonment both are nouns.

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

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

penalty (noun)	imprisonment (noun)
the act of punishing, or the infliction of a penalty	the act of confining someone in a prison (or as if in a prison)
the disadvantage or painful consequences of an action or condition	putting someone in prison or in jail as lawful punishment
(games) a handicap or disadvantage that is imposed on a competitor (or a team) for an infraction of the rules of the game	the state of being imprisoned
a payment required for not fulfilling a contract