Learn how to say Facultatively correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word facultative:
occurring optionally in response to circumstances rather than by nature:
facultative adjustment in relation to competitive abilities
Biology capable of but not restricted to a particular function or mode of life:
a facultative parasite
Often contrasted with obligate.
early 19th century: from French facultatif, -ive, from faculté (see faculty)