voluntary vs willful

voluntary is a noun but willful is not a noun.

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

voluntary (noun)	willful (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

voluntary (adjective)	willful (adjective)
of your own free will or design; done by choice; not forced or compelled	habitually disposed to disobedience and opposition
controlled by individual volition	done by design