facultative, a. [L. facultas, -atis, faculty: cf. F. facultatif, G. fakultativ.].
Having relation to the grant or exercise faculty, or authority, privilege, license, or the like hence, optional; as, facultative enactments, or those which convey a faculty, or permission; the facultative referendum of Switzerland is one that is optional with the people and is necessary only when demanded by petition; facultative studies; -- opposed to obligatory and compulsory, and sometimes used with to. [Webster 1913 Suppl.]
Of such a character as to admit of existing under various forms or conditions, or of happening or not happening, or the like; [Webster 1913 Suppl.]
Pertaining to a faculty or faculties.
"In short, there is no facultative plurality in the mind; it is a single organ of true judgment for all purposes, cognitive or practical."
[Webster 1913 Suppl.]
facultative, adj.
1 Law enabling an act to take place.
2 that may occur.
3 Biol. not restricted to a particular function, mode of life, etc.
4 of a faculty.