necessary

1 forcing one's compliance or participation by or as if by law an emissions test is necessary before you can renew the registration for your car Synonyms compulsory, forced, imperative, incumbent, involuntary, mandatory, nonelective, obligatory, peremptory, requiredRelated Words all-important, essential, indispensable, needed, requisite; insistent, persistent, pressing, urgent; demanded, enforced; coerciveNear Antonyms chosen, discretionary; dispensable, unnecessary, unneeded, unwanted; inconsequential, insignificant, nonessential, unimportantAntonyms elective, optional, voluntary

2 impossible to avoid or evade taxes will always be a necessary evil Synonyms certain, ineluctable, ineludible, inescapable, inevitable, sure, unavoidable, unescapableRelated Words decided, definite, settled; likely, possible, probable; destined, fated, foreordained, predestined, predetermined, preordained; inexorable, relentless, unremitting, unstoppableNear Antonyms preventable (also preventible); doubtful, dubious, questionable, shaky, unclear; undecided, unsettled; undependable, unreliable; improbable, unlikelyAntonyms avoidable, evadable, uncertain, unsure

3 impossible to do without food and water are necessary for survival Synonyms all-important, critical, imperative, indispensable, integral, must-have, essential, necessitous, needed, needful, required, requisite, vitalRelated Words prerequisite; compulsory, mandatory, nonelective, obligatory; consequential, crucial, important, major, material, meaningful, momentous, significant, substantial, weighty; basic, central, fundamental, key, organic; insistent, persistent, pressing, urgentNear Antonyms undesired, unwanted; inconsequential, insignificant, unimportant; excess, external, extra, extraneous, superfluous, surplusAntonyms dispensable, inessential, needless, nonessential, unessential, unnecessary, unneeded