dependent vs underage

dependent is a noun but underage is not a noun.

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

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

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