Synonyms for Elective (same or very similar meaning)
WordNet sense 1 (possible but not necessary; left to personal choice):
optionalWordNet sense 2 (relating to or composed of electors):
electoralWordNet sense 3 (subject to popular election):
electedWordNet sense 4 (a course that the student can select from among alternatives):
elective courseFrom the ODE community, based on WordNetadd/edit