obligatory Antonyms

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