changeling vs youngster

changeling and youngster both are nouns.

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

As nouns, youngster is a hypernym of changeling; that is, youngster is a word with a broader meaning than changeling:

Other hypernyms of changeling include child, fry, kid, minor, nestling, nipper, shaver, small fry, tiddler, tike, tyke.

changeling (noun)	youngster (noun)
a child secretly exchanged for another in infancy	a young person of either sex
a person of subnormal intelligence