nudity vs undress

nudity and undress both are nouns.

Word	Noun	Adjective	Verb	Adverb
nudity	Yes	No	No	No
undress	Yes	No	Yes	No

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

Other hyponyms of nudity include nude, altogether, birthday suit, raw, bareness.

nudity (noun)	undress (noun)
the state of being without clothing or covering of any kind	partial or complete nakedness

nudity (verb)	undress (verb)
	get undressed
	remove (someone's or one's own) clothes