term:

Elective

elective adj

1 a : chosen by popular election [an official]
b : of or relating to election
c : based on the right or principle of election [the presidency is an office]
2 a : permitting a choice compare compulsory
b : available as a choice [ insurance coverage]
c : beneficial to the patient but not essential for survival [ surgery]

Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.