youngster vs peanut

youngster and peanut both are nouns.

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

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

youngster (noun)	peanut (noun)
a young person of either sex	pod of the peanut vine containing usually 2 nuts or seeds; `groundnut' and `monkey nut' are British terms
	a young child who is small for his age
	widely cultivated American plant cultivated in tropical and warm regions; showy yellow flowers on stalks that bend over to the soil so that seed pods ripen underground
	underground pod of the peanut vine

youngster (adjective)	peanut (adjective)
	of little importance or influence or power; of minor status