from The American Heritage® Dictionary of the English Language, 4th Edition

  • 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.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • 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

from the GNU version of the Collaborative International Dictionary of English

  • 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.

from The Century Dictionary and Cyclopedia

  • 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.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • 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


Sorry, no etymologies found.


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

    Human Family Walks on All Fours

  • Most of the bacteria which produce disease are facultative, that is, they grow either with or without oxygen; but certain of them, as the bacillus of tetanus, are anaërobic.

    Disease and Its Causes

  • In some cantons the referendum is obligatory, in others it is "facultative," or optional.

    The Governments of Europe

  • I don't know if it's more to do with me (that is, if I express emotion differently in one language more than the other, that is, if English is my critical/facultative language and Spanish my emotional language) or the fact of Spanish being one of those languages with a formal (usted) and informal (tu) second person.

    Breakfast in Bed

  • However, the increased estuarine production discussed previously will possibly offset any tendency to reduce facultative anadromy in response to increased freshwater production.

    Effects of climate change on arctic anadromous fish

  • Something I've not yet commented on since my part facultative-festive and part enforced-technological break is the welcome restoration of sense and good legal analysis to the field of religious discrimination by the Employment Appeal Tribunal, which has reversed the much-publicised but obviously wrong decision at first instance in this case.

    Archive 2009-01-01

  • In the same way we greet as a positive element the possibility – permitted as a facultative choice by the motu proprio – of proclaiming, in the old rite, the readings in the vernacular.

    Archive 2009-07-01

  • The host (facultative aerobe implies facultative anaerobe, doesn't it?) could handle aerobic conditions already, presumably because it had peroxisomes as oxygen sink. t's funny that you mention peroxisomes, as people once thought they were endosymbionts but now evidence seems to point to en origin from the ER.

    A critique on the endosymbiotic theory for the origin of mitochondria

  • Maybe you mean facultative anaerobic in the sense that the host had peroxisomes in order to prevent itself to the harmful effects of reactive oxygen species.

    A critique on the endosymbiotic theory for the origin of mitochondria

  • The original "slave" might have been photosynthetic, while the "host" might have been a facultative aerobe thanks to peroxisomes.

    A critique on the endosymbiotic theory for the origin of mitochondria


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