necessary Synonyms

essential requisite needed critical unavoidable vital imperative indispensable mandatory crucial required obligatory key necessity prerequisite requirement fundamental integral important needful incumbent inevitable ineluctable inescapable binding compulsory basic prescribed life-or-death pressing prime life-and-death ratiocinative relevant comfort station de rigueur predetermined predestined nonoptional must-have organic paramount perforce pivotal plasmic precondition mandated principal amoebic of the essence