UK:*UK and possibly other pronunciationsUK and possibly other pronunciations/ˈnɛsəsəri/US:USA pronunciation: IPA and respellingUSA pronuncation: IPA/ˈnɛsəˌsɛri/ ,USA pronunciation: respelling(nes′ə ser′ē)
essential; needed; unavoidable:a small but necessary change in our plans.[It + be + ~ + that clause]:It is necessary that you stay until the end of the meeting.[It + be + ~ (+ for + object) + to + verb]It isn't necessary (for you) to stay.
necessary is an adjective, necessity is a noun, necessitate is a verb:He carried only what was necessary for survival. He carried a few necessities with him. The invasion necessitates a quick response on our part.
being essential, indispensable, or requisite:a necessary part of the motor.
happening or existing by necessity:a necessary change in our plans.
acting or proceeding from compulsion or necessity; not free; involuntary:a necessary agent.
(of a proposition) such that a denial of it involves a self-contradiction.
(of an inference or argument) such that its conclusion cannot be false if its supporting premises are true.
(of a condition) such that it must exist if a given event is to occur or a given thing is to exist. Cf. sufficient (def. 2).
something necessary or requisite; necessity.
Lawnecessaries, food, clothing, etc., required by a dependent or incompetent and varying with his or her social or economic position or that of the person upon whom he or she is dependent.
Dialect Terms[Chiefly New Eng.]a privy or toilet.
Latin necessārius unavoidable, inevitable, needful, equivalent. to necess(e) (neuter indeclinable adjective, adjectival) unavoidable, necessary + -ārius -ary
Middle English necessarie 1300–50
1.See corresponding entry in Unabridged required, needed. Necessary,essential,indispensable,requisite indicate something vital for the fulfillment of a need. Necessary applies to that without which a condition cannot be fulfilled or to an inevitable consequence of certain events, conditions, etc.:Food is necessary to life. Multiplicity is a necessary result of division.Indispensable applies to something that cannot be done without or removed from the rest of a unitary condition:Food is indispensable to living things. He made himself indispensable as a companion.That which is essential forms a vitally necessary condition of something:Air is essential to red-blooded animals. It is essential to understand the matter clearly.Requisite applies to what is thought necessary to fill out, complete, or perfect something:She had all the requisite qualifications for a position.
5.See corresponding entry in Unabridged requirement, requisite, essential.
1.See corresponding entry in Unabridged dispensable.