Definition

1. Adjective:
   • Optional, not compulsory: Describes something that is not required or mandatory, but can be chosen.
   • Granting permission or authority: Relating to a law, rule, or enactment that gives a privilege or the power to choose whether to do something or not.
   • Able to exist under varying conditions: In biology, describes an organism that can live in different modes or environments, not being restricted to one.
   • Relating to mental faculties: Pertaining to the powers or capacities of the mind.

Usage Examples

• Adjective:
  • The university offers several facultative courses in arts and humanities.
  • The new regulation is facultative, allowing companies to adopt the standard if they wish.
  • A facultative anaerobe is a bacterium that can grow with or without oxygen.
  • The philosopher discussed the facultative powers of human reason and imagination.

Advanced Usage

• In legal/formal contexts: Used to describe permissive, non-mandatory clauses.
  • The treaty included a facultative protocol that member states could ratify separately.
• In biology/ecology: Specifically describes an organism's adaptability.
  • Unlike obligate parasites, facultative parasites do not require a host to complete their life cycle.

Variants and Related Words

• Facultatively (adverb): In an optional or adaptable manner.
  • The bacteria can live facultatively in aerobic conditions.
• Facultativity (noun, rare): The quality of being facultative.

Synonyms

• Optional
• Discretionary
• Permissive
• Non-compulsory
• Elective (specifically for courses)

Antonyms

• Obligatory
• Compulsory
• Mandatory
• Required

Related Phrases/Concepts

• Facultative anaerobe: A microorganism that makes ATP by aerobic respiration if oxygen is present but is capable of switching to fermentation or anaerobic respiration if oxygen is absent.
• Facultative parasite: An organism that normally lives independently but can become parasitic under certain conditions.
• Facultative provision: A clause in a contract or treaty that is not binding but can be activated.

Adjective

1. not compulsory
   • facultative courses in the sciences
2. granting a privilege or permission or power to do or not do something
   • a facultative enactment
3. able to exist under more than one set of conditions
   • a facultative parasite can exist as a parasite or a saprophyte
4. of or relating to the mental faculties