Definition of: necessary

(nes′ə·ser′ē) adjective
1. Being such in its nature or conditions that it must exist, occur, or be true; inevitable.
2. Absolutely needed to accomplish a desired result; essential; requisite.
3. Compulsory: a necessary action.
4. Being such that it must be believed.
5. Archaic Rendering useful and intimate service.
—noun plural ·sar·ies
1. That which is indispensable; an essential requisite: used usually in the plural: the necessaries of life.
2. That which is subject to the law of necessity: The necessary is opposed to the contingent.
3. A watercloset; privy. [<L necessarius necessary]
—nec′es·sar′i·ly adverb
—nec′es·sar′i·ness noun Synonyms (adj.): compulsory, essential, indispensable, inevitable, needed, needful, required, requisite, unavoidable, undeniable. That which is essential belongs to the essence of a thing, so that the thing cannot exist in its completeness without it; that which is indispensable may be only an adjunct, but it is one that cannot be spared. That which is requisite is so in the judgment of the person requiring it. Food is necessary, death is inevitable; a necessary conclusion satisfies a thinker; an inevitable conclusion silences opposition. Needed and needful are more concrete than necessary, and respect an end to be attained, while necessary may apply simply to what exists; we speak of a necessary inference; necessary food is what one cannot live without, while needful food is that without which we cannot enjoy comfort, health, and strength. Antonyms: casual, contingent, needless, non-essential, optional, unnecessary, useless, worthless.