juvenile vs jejune

juvenile is a noun but jejune is not a noun.

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

As adjectives, juvenile and jejune are synonyms defined as:

Other synonyms of juvenile include adolescent, puerile.

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

juvenile (adjective)	jejune (adjective)
of or relating to or characteristic of or appropriate for children or young people	displaying or suggesting a lack of maturity
displaying or suggesting a lack of maturity	of insufficient quantity to meet a need
	lacking interest or significance or impact