youngster vs nipper

youngster and nipper both are nouns.

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

As nouns, youngster and nipper are synonyms defined as:

Other synonyms of youngster include child, fry, kid, minor, nestling, shaver, small fry, tiddler, tike, tyke.

youngster (noun)	nipper (noun)
a young person of either sex	a grasping structure on the limb of a crustacean or other arthropods
	a young person of either sex