The present disambiguation page holds the title of a primary topic, and an article needs to be written about it. It is believed to qualify as a broad-concept article. It may be written directly at this page or drafted elsewhere and then moved over here. Related titles should be described in Facultative, while unrelated titles should be moved to Facultative (disambiguation).
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Facultative means "optional" or "discretionary" (antonym obligate), used mainly in biology in phrases such as: