not required

discretional discretionary elective noncompulsory nonobligatory volitional voluntary

alternative arbitrary discretional discretionary elective extra facultative free no strings attached noncompulsory nonobligatory open unforced unrestricted up to the individual volitional voluntary

compulsory forced required

accidental avoidable fortuitous futile inappropriate inessential needless nonessential optional unessential uninvited unneeded unrequired unwanted unwarranted unwelcome useless