youngster vs small fry

youngster and small fry both are nouns.

Word	Noun	Adjective	Verb	Adverb
youngster	Yes	No	No	No
small fry	Yes	No	No	No

As nouns, youngster and small fry are synonyms defined as:

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

youngster (noun)	small fry (noun)
a young person of either sex	someone who is small and insignificant
	a young person of either sex