elective
1. elec.tive \i-'lek-tiv\ aj 1a: chosen or filled by popular election 1b: of or relating to election 1c: based on the right or principle of election 2: permitting a choice : OPTIONAL 3a: tending to operate on one substance rather than another 3b: favorably inclined : SYMPATHETIC - elec.tive.ly av 2. elec.tive n : an elective course or subject