necessary Synonyms

requisite essential needed crucial prerequisite requirement required imperative incumbent indispensable obligatory ineluctable inescapable inevitable integral key mandatory needful critical unavoidable necessity binding vital compulsory mandated indispensableness predestined amoebic precondition comfort station plasmic pivotal perforce life-and-death paramount need unpreventable of the essence life-or-death de rigueur needs organic predetermined all important take substantive structural right-hand returnless underlying