1 of or relating to the mental faculties
2 able to exist under more than one set of conditions; "a facultative parasite can exist as a parasite or a saprophyte" [ant: obligate]
3 granting a privilege or permission or power to do or not do something; "a facultative enactment"
4 not compulsory; "facultative courses in the sciences"
- Free Medical Dictionary
- Oxford English Dictionary