Synonyms of the word

optional

• adj. Not compulsory; left to personal choice; elective.
• n. Something that is not compulsory, especially part of an academic course.
• n. (programming) In the Swift programming language, a kind of variable that is assigned a specific data type…

elective

• adj. Of, or pertaining to voting or elections.
• adj. That involves a choice between options; optional or discretionary.
• n. Something that is option or that may be elected, like a course of tertiary study or a medical procedure.

facultative

• adj. Of or relating to faculty, especially to mental faculty.
• adj. Not obligate; optional, discretionary or elective.
• adj. That grants permission or power to do something.
• adj. (biology) Able to perform a particular life function, or to live generally, in more than one way.
• adj. (geometry, of a point) At which a given function is positive.

nonmandatory

• adj. Not mandatory.

nonobligatory

• adj. not obligatory; not required; optional.