facultative

American  

[fak-uhl-tey-tiv] / ˈfæk əlˌteɪ tɪv /

adjective

1. conferring a faculty, privilege, permission, or the power of doing or not doing something.

   a facultative enactment.

2. left to one's option or choice; optional.

   The last questions in the examination were facultative.

3. that may or may not take place; that may or may not assume a specified character.

4. Biology. having the capacity to live under more than one specific set of environmental conditions, as a plant that can lead either a parasitic or a nonparasitic life or a bacterium that can live with or without air (opposed to obligate).

5. of or relating to the faculties.

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facultative British  

/ ˈfækəltətɪv /

adjective

1. empowering but not compelling the doing of an act

2. philosophy that may or may not occur

3. insurance denoting a form of reinsurance in which the reinsurer has no obligation to accept a particular risk nor the insurer to reinsure, terms and conditions being negotiated for each reinsurance

4. biology able to exist under more than one set of environmental conditions Compare obligate

   a facultative parasite can exist as a parasite or a saprotroph

5. of or relating to a faculty

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facultative Scientific  

/ făk′əl-tā′tĭv /

1. Capable of existing under varying environmental conditions or by assuming various behaviors. Bacteria that are facultative aerobes can live in both aerobic and anaerobic environments. A facultative parasite can live independently of its usual host.

2. Compare obligate

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Other Word Forms

• facultatively adverb
• nonfacultative adjective

Etymology

Origin of facultative

First recorded in 1820-25; from French facultative (feminine) “conveying or granting a right or power,” from faculté “knowledge, learning, physical or moral capacity,” ultimately from Latin facultāt-, the stem of facultās (originally a doublet of the noun facilitās “ease, ease of performance or completion, facility”) “ability, power, capacity” + -ative adjective suffix; see faculty ( def. ), -ive ( def. )

Example Sentences

Some require fertilization to produce seeds, while others can also reproduce without fertilization, a process known as facultative agamospermy.

From Science Daily • Dec. 20, 2025

However, there remain many unknowns about parthenogenesis, particularly the form known as facultative parthenogenesis, which is quite rare and only happens in animals that sexually reproduce.

From Salon • Jul. 28, 2023

Note that there is no clear line that differentiates facultative carnivores from omnivores; dogs would be considered facultative carnivores.

From Textbooks • Jun. 9, 2022

On the issue of facultative reinsurance, whereby it insures bundles of risk in a job lot, Swiss Re said it expected to finalise a policy for the oil and gas sector in 2023.

From Reuters • Mar. 17, 2022

Ewart's important discovery that some of these lipochrome pigments occlude oxygen, while others do not, may have bearings on the facultative anaerobism of these organisms.

From Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 2 "Baconthorpe" to "Bankruptcy" by Various