Synonyms for necessary

modified

1. Essential

   essential, requisite, expedient, needful, indispensable, needed, required, urgent, wanted, imperative, prerequisite, exigent, pressing, vital, cardinal, fundamental, significant, momentous, compulsory, mandatory, basic, paramount, obligatory, essential, compelling, incumbent on, incumbent upon, all-important, nuts-and-bolts, binding, specified, unavoidable, decisive, crucial, elementary, quintessential, chief, principal, prime, intrinsic, fixed, constant, permanent, determinate, inherent, ingrained, innate, without choice, without appeal; see also important 1.

   Antonyms unimportant*, unessential, insignificant.

2. Inevitable

   unavoidable, undeniable, assured; see certain 2, imminent, inevitable.