adj. & n.
--adj.
1. requiring to be done, achieved, etc.; requisite, essential (it is necessary to work; lacks the necessary documents).
2 determined, existing, or happening by natural laws, predestination, etc., not by free will; inevitable (a necessary evil).
3 Philos. (of a concept or a mental process) inevitably resulting from or produced by the nature of things etc., so that the contrary is impossible.
4 Philos. (of an agent) having no independent volition.
--n. (pl. -ies) (usu. in pl.) any of the basic requirements of life, such as food, warmth, etc.
Phrases and idioms:
the necessary colloq.
1. money.
2 an action, item, etc., needed for a purpose (they will do the necessary).
Etymology: ME f. OF necessaire f. L necessarius f. necesse needful