juvenile vs immature

juvenile is a noun but immature is not a noun.

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

juvenile (noun)	immature (noun)
a young person, not fully developed

juvenile (adjective)	immature (adjective)
of or relating to or characteristic of or appropriate for children or young people	not yet mature
displaying or suggesting a lack of maturity	characteristic of a lack of maturity
	(used of living things especially persons) in an early period of life or development or growth
	(of birds) not yet having developed feathers
	not fully developed or mature; not ripe