underage vs dependent

underage is not a noun while dependent is a noun.

Word	Noun	Adjective	Verb	Adverb
underage	No	Yes	No	No
dependent	Yes	Yes	No	No

underage (noun)	dependent (noun)
	a person who relies on another person for support (especially financial support)

underage (adjective)	dependent (adjective)
not of legal age	relying on or requiring a person or thing for support, supply, or what is needed
dependent by virtue of youth	(of a clause) unable to stand alone syntactically as a complete sentence
	addicted to a drug
	contingent on something else
	being under the power or sovereignty of another or others
	held from above and hanging down