Necessary, a.
Etymology: [L. necessarius, from necesse unavoidable, necessary; of uncertain origin: cf. F. nécessaire.]
1. Such as must be; impossible to be otherwise; not to be avoided; inevitable. Death, a necessary end, Will come when it will come. Shak.
2. Impossible to be otherwise, or to be dispensed with, without preventing the attainment of a desired result; indispensable; requiste; essential. "'T is necessary he should die." Shak. A certain kind of temper is necessary to the pleasure and quiet of our minds. Tillotson.
3. Acting from necessity or compulsion; involuntary; -- opposed to free; as, whether man is a necessary or a free agent is a question much discussed.
1 other Webster entry under this spelling
Necessary, n.; pl. Necessaries (.
1. A thing that is necessary or indispensable to some purpose; something that one can not do without; a requisite; an essential; -- used chiefly in the plural; as, the necessaries of life.
2. A privy; a water-closet.
3. pl. (Law)
Such things, in respect to infants, lunatics, and married women, as are requisite for support suitable to station.
Shades of meaning
That is necessary which must exist, occur, or be true; which in the nature of things can not be otherwise. That which is essential belongs to the essence of a thing, so that the thing can not exist in its completeness without it; that which is indispensable may be only an adjunct, but it is one that can not be spared; vigorous health is essential to an arctic explorer; warm clothing is indispensable. That which is requisite (or required) is so in the judgment of the person requiring it, but may not be so absolutely; thus, the requisite is more a matter of personal feeling than the indispensable. Inevitable (L. in, not, and evito, shun) is primarily the exact equivalent of the Saxon unavoidable; both words are applied to things which some at least would escape or prevent, while that which is necessary may meet with no objection; food is necessary, death is inevitable; a necessary conclusion satisfies a thinker; an inevitable conclusion silences opposition. An infallible proof is one that necessarily leads the mind to a sound conclusion. Needed and needful are more concrete than necessary, and respect an end to be attained; we speak of a necessary inference; necessary food is what one can not live without, while needful food is that without which he can not enjoy comfort, health, and strength.
Prepositions
Necessary to a sequence or a total; for or to a result or a person; unity is necessary to (to constitute) completeness; decision is necessary for command, or for a commander.