"elective" in the noun sense
1. elective course, elective
a course that the student can select from among alternatives
"elective" in the adjective sense
1. elective, elected
subject to popular election
"elective official"
2. elective, facultative
not compulsory
"elective surgery"
"an elective course of study"
Source: WordNet® (An amazing lexical database of English)
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