This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Of or relating to a mental faculty.

adj. Capable of occurring or not occurring; contingent.

adj. Not required or compulsory; optional.

adj. Granting permission or authority.

adj. Biology Capable of functioning under varying environmental conditions. Used of certain organisms, such as bacteria that can live with or without oxygen.

adj. Of or relating to faculty, especially to mental faculty

adj. Not obligate; optional, discretionary or elective

adj. That grants permission or power to do something

adj. Able to grow in or outside of a host or host cell

adj. Having relation to the grant or exercise faculty, or authority, privilege, license, or the like hence, optional; -- opposed to obligatory and compulsory, and sometimes used with to.

adj. Of such a character as to admit of existing under various forms or conditions, or of happening or not happening, or the like

adj. Pertaining to a faculty or faculties.

Conferring a faculty, right, or power; enabling.

Hence Conferring the power of doing or not doing; rendering optional or contingent.

Having a faculty or power, but exercising it only occasionally or incidentally, or failing to exercise it; occasional or incidental; optional or contingent. Compare obligate.

adj. able to exist under more than one set of conditions

adj. not compulsory

adj. granting a privilege or permission or power to do or not do something

adj. of or relating to the mental faculties

"The Turkish children featured in the documentary show what I'd call facultative quadrupedalism; they walk on all fours out of necessity."

optional    enabling   

obligatory    compulsory    obligate   

facultative saprophyte    facultative parasite    facultative hypermetropia   

facultatively   

optional   

nitrogen-fixing    partial-birth    them.the    voucher-based    food-poisoning    criminalized    multidrug-resistant    rod-shaped    useof    antenatal