unpaid vs voluntary

unpaid is not a noun while voluntary is a noun.

Word	Noun	Adjective	Verb	Adverb
unpaid	No	Yes	No	No
voluntary	Yes	Yes	No	No

unpaid (noun)	voluntary (noun)
	composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a religious service or musical performance
	(military) a person who freely enlists for service

unpaid (adjective)	voluntary (adjective)
not paid	of your own free will or design; done by choice; not forced or compelled
engaged in as a pastime	controlled by individual volition
without payment