Of or relating to faculty, especially to mental faculty (adjective)
Not obligate; optional, discretionary or elective (adjective)
That grants permission or power to do something (adjective)
Able to grow in or outside of a host or host cell (adjective)
Examples of word facultative
The Turkish children featured in the documentary show what I'd call facultative quadrupedalism; they walk on all fours out of necessity.
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.
In some cantons the referendum is obligatory, in others it is "facultative," or optional.
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.
However, the increased estuarine production discussed previously will possibly offset any tendency to reduce facultative anadromy in response to increased freshwater production.