obligatory Antonyms

optional going begging backup uncoerced unnecessary irrelevant unimportant willful voluntary voluntarily volitional useless unessential tautologic surplus supplanter supernumerary fill-in locum meter maid witting unwanted unrequired unconsumed spare part non-compulsory unneeded fallback facultative expendable non-essential elidable de trop amexed nonobligatory nonmandatory superfluous substitutive emergency elective disposable dispensable discretionary discretional deliberate avoidable avertible auxiliary ascititious another