juvenile vs nipper

juvenile and nipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
juvenile	Yes	Yes	No	No
nipper	Yes	No	No	No

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

juvenile (noun)	nipper (noun)
a young person, not fully developed	a grasping structure on the limb of a crustacean or other arthropods
	a young person of either sex

juvenile (adjective)	nipper (adjective)
of or relating to or characteristic of or appropriate for children or young people
displaying or suggesting a lack of maturity