1. 由选举产生的;选任的
An elective post or committee is one to which people are appointed as a result of winning an election.

2. （外科手术）非急需的，可选择的
Elective surgery is surgery that you choose to have before it becomes essential.

3. 选修课
An elective is a subject which a student can choose to study as part of his or her course.

1. a course that the student can select from among alternatives

Synonym: elective course