necessary

[ nes-uh-ser-ee ]
/ ˈnɛs əˌsɛr i /

adjective

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.
Logic.
  1. (of a proposition) such that a denial of it involves a self-contradiction.
  2. (of an inference or argument) such that its conclusion cannot be false if its supporting premises are true.
  3. (of a condition) such that it must exist if a given event is to occur or a given thing is to exist.Compare sufficient(def 2).

noun, plural nec·es·sar·ies.

Origin of necessary

1300–50; Middle English necessarie < Latin necessārius unavoidable, inevitable, needful, equivalent to necess(e) (neuter indeclinable adj.) unavoidable, necessary + -ārius -ary

SYNONYMS FOR necessary

1 required, needed. Necessary, essential, indispensable, requisite indicate something vital for the fulfillment of a need. Necessary applies to something 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. Something that 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 requirement, requisite, essential.

Related forms

nec·es·sar·i·ness, nounqua·si-nec·es·sar·y, adjective

Can be confused

necessary necessitous (see synonym study at the current entry)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for necessary

British Dictionary definitions for necessary

necessary

/ (ˈnɛsɪsərɪ) /

adjective

noun

the necessary informal the money required for a particular purpose
do the necessary informal to do something that is necessary in a particular situation
See also necessaries

Word Origin for necessary

C14: from Latin necessārius indispensable, from necesse unavoidable
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012