juvenile person vs somebody

juvenile person and somebody both are nouns.

Word	Noun	Adjective	Verb	Adverb
juvenile person	Yes	No	No	No
somebody	Yes	No	No	No

As nouns, somebody is a hypernym of juvenile person; that is, somebody is a word with a broader meaning than juvenile person:

juvenile person: a young person, not fully developed
somebody: a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential

Other hypernyms of juvenile person include individual, mortal, person, someone, soul.

juvenile person (noun)	somebody (noun)
a young person, not fully developed	a human being; person, singular, assertive existential pronoun; pronoun, person, singular; quantifier: assertive existential