voluntary vs physiology

voluntary and physiology both are nouns.

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

voluntary (noun)	physiology (noun)
composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a religious service or musical performance	processes and functions of an organism
(military) a person who freely enlists for service	the branch of the biological sciences dealing with the functioning of organisms

voluntary (adjective)	physiology (adjective)
of your own free will or design; done by choice; not forced or compelled
controlled by individual volition