Từ trái nghĩa của optional

Từ đồng nghĩa: elective, voluntary,

Từ trái nghĩa: compulsory,

compulsory essential mandatory necessary enforced obligatory required compulsatory requisite unavoidable incumbent inescapable forced nonvoluntary set imperative prescribed enforceable peremptory nonelective contractual statutory binding stipulated de rigueur involuntary nondiscretionary compelled unwilled appointed will-less coerced needed indispensable needful unintentional nondeliberate nonpurposive conscripted instinctive automatic unwilling

essential necessary needed required compulsory indispensable obligatory basic crucial vital designed pivotal imperative needful careful central critical acute mandatory requisite fundamental key pressing important urgent compelling consequential planned paramount prerequisite significant integral necessitous substantive all important all-important de rigueur high-priority life-and-death must-have pre-eminent vitally important of great consequence of the essence of the utmost importance core compulsatory elementary burning useful intrinsic appropriate recommended exigent rudimentary principal demanded cardinal valuable inherent innate desired worthwhile incumbent called for

primary core fundamental principal chief key main premier prime principle capital central dominant greater intrinsic major predominant underlying arch cardinal characteristic crucial elementary essential focal head overriding pivotal preeminent prominent root staple basal basic critical elemental first foremost highest lead leading master paramount prevailing quintessential sovereign supreme top true ultimate vital commanding controlling foundational grand greatest high natural presiding primordial rudimentary ruling salient strongest superordinate number-one pre-eminent strong number one numero uno most important

regular

optional curriculum optional extra optionalize optionally optional session optional subject option opting out of opting out opting in opting opt-in