|a.||1.||Having relation to the grant or exercise faculty, or authority, privilege, license, or the like hence, optional; |
|2.||(Biol.) Of such a character as to admit of existing under various forms or conditions, or of happening or not happening, or the like;|
|3.||(Physiol.) Pertaining to a faculty or faculties.|
|Adj.||1.||facultative - of or relating to the mental faculties|
|2.||facultative - able to exist under more than one set of conditions; "a facultative parasite can exist as a parasite or a saprophyte"|
obligate - restricted to a particular condition of life; "an obligate anaerobe can survive only in the absence of OXYGen"
|3.||facultative - granting a privilege or permission or power to do or not do something; "a facultative enactment"|
|4.||facultative - not compulsory; "facultative courses in the sciences"|