pertaining to the principle of electing to an office, position, etc.

chosen by election, as an official.

bestowed by or derived from election, as an office.

having the power or right of electing to office, as a body of persons.

open to choice; optional; not required

an elective subject in college; elective surgery.

Chemistry . selecting for combination or action; tending to combine with certain substances in preference to others

elective attraction.

an optional study; a course that a student may select from among alternatives.

adjective

required

adjective

constituent , discretionary , electoral , facultative , nonobligatory , not compulsory , optional , selective , voluntary , voting