facultative

From French facultatif.^[1] By surface analysis, faculty +‎ -ative.

• (Received Pronunciation) IPA^(key): /ˈfæ.kəl.tə.tɪv/
• (General American) IPA^(key): /ˈfæ.kəlˌteɪ.tɪv/

• Audio (US):

  (file)

• Hyphenation: fac‧ul‧ta‧tive

facultative (comparative more facultative, superlative most facultative)

1. Of or relating to faculty, especially to mental faculty.
2. Not obligate; optional, discretionary or elective.

   Synonyms: see Thesaurus:optional

   Antonyms: see Thesaurus:requisite

   • 1953, Samuel Beckett, Watt, 1st American edition, New York, N.Y.: Grove Press, published 1959, →OCLC:

     But does the penny fare end here, said Mr. Nixon, at a merely facultative stop? Surely it ends rather at the station.

   • 2020, Jonathan Mance et al., editors, Insurance Disputes, Taylor & Francis, →ISBN, page 584:

     The policy would be a “facultative” policy, whereby the insurers would first have assessed the risk involved in the particular shipment and decided to accept it.

3. That grants permission or power to do something.
4. (biology) Able to perform a particular life function, or to live generally, in more than one way.

   Antonym: obligate

   facultative feeder

   • 1993, Hachiro Oku, Plant Pathogenesis and Disease Control, CRC Press, →ISBN, page 10:

     This hypothesis might be supported by the evidence that there are varieties of pathogenic fungi of which parasitism is in varying degrees, between obligate parasitic and facultative parasitic. The facultative parasite, which usually lives as a saprophyte but under some conditions can parasitize on a plant, seems to be a pathogen with the lowest parasitic adaptation.

5. (geometry, of a point) At which a given function is positive.
   • 1866, George Salmon, Lessons Introductory to the Modern Higher Algebra, Dublin: Hodges, Smith, and Co., page 197:

     For then it is seen, as before, that it is the points outside the two sheets which are facultative, and not the points between the surface and the touching plane.

• facultatively

• Free Medical Dictionary

• active fault

• IPA^(key): /fa.kyl.ta.tiv/

facultative

1. feminine singular of facultatif