juvenile vs preteenager

juvenile and preteenager both are nouns.

Word	Noun	Adjective	Verb	Adverb
juvenile	Yes	Yes	No	No
preteenager	Yes	No	No	No

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

juvenile: a young person, not fully developed
preteenager: a preadolescent boy or girl (usually between 9 and 12 years of age)

juvenile (noun)	preteenager (noun)
a young person, not fully developed	a preadolescent boy or girl (usually between 9 and 12 years of age)

juvenile (adjective)	preteenager (adjective)
of or relating to or characteristic of or appropriate for children or young people
displaying or suggesting a lack of maturity