voluntary
adjective
- 1
of your own free will or design; done by choice; not forced or compelled
man is a voluntary agent
participation was voluntary
- 2
controlled by individual volition
voluntary motions
voluntary muscles
noun
- 1
composition (often improvised) for a solo instrument (especially solo organ) and not a regular part of a religious service or musical performance
- 2
(military) a person who freely enlists for service
Synonyms
Also useful for “voluntary”:Scrabble— High-value letters — see what it scores