necessary

American  

[nes-uh-ser-ee] / ˈnɛs əˌsɛr i /

adjective

1. essential, indispensable, or requisite.

   The rotor is a necessary part of the motor.

   Synonyms:

   needed

   Antonyms:

   dispensable

2. happening or existing by necessity.

   The snow has forced a necessary change in our plans.

3. acting or proceeding from compulsion or necessity; not free; involuntary.

   a necessary agent.

4. 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.

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noun

plural

necessaries

1. something necessary or required for a particular purpose; necessity.

   Synonyms:

   essential, requisite, requirement

2. Law. necessaries, food, clothing, etc., required by a dependent person and varying with their social or economic position or that of the person upon whom they are dependent.

3. Chiefly New England. a privy or toilet.

necessary British  

/ ˈnɛsɪsərɪ /

adjective

1. needed to achieve a certain desired effect or result; required

2. resulting from necessity; inevitable

   the necessary consequences of your action

3. logic

   1. (of a statement, formula, etc) true under all interpretations or in all possible circumstances

   2. (of a proposition) determined to be true by its meaning, so that its denial would be self-contradictory

   3. (of a property) essential, so that without it its subject would not be the entity it is

   4. (of an inference) always yielding a true conclusion when its premises are true; valid

   5. (of a condition) entailed by the truth of some statement or the obtaining of some state of affairs Compare sufficient

4. philosophy (in a nonlogical sense) expressing a law of nature, so that if it is in this sense necessary that all As are B, even although it is not contradictory to conceive of an A which is not B, we are licensed to infer that if something were an A it would have to be B

5. rare compelled, as by necessity or law; not free

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noun

1. informal the money required for a particular purpose

2. informal to do something that is necessary in a particular situation

Related Words

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.

Other Word Forms

• necessariness
  noun
• quasi-necessary
  adjective

Etymology

Origin of necessary

First recorded in 1300–50; Middle English necessarie, from Latin necessārius “unavoidable, inevitable, needful,” equivalent to necess(e) (neuter indeclinable adjective) “unavoidable, necessary” + -ārius -ary

Explanation

Everyone can agree that certain things are necessary for survival: food, water, shelter. Some people might add chocolate to that list. Necessary refers to anything you can't do without. Necessary, cede, and cease all come from the same root, cedere, which is Latin for "to go away" or "to give something up." When something's necessary, you won't give it up. That fudge-covered brownie sundae from your favorite ice-cream shop? It might seem like a decadent treat, but if you're a true chocolate lover you'll insist that it's as necessary as a warm jacket in winter.

Example Sentences

Some farmers argue the chemical is necessary but the Soil Association warns that its use as a drying agent leaves residues in foods such as bread, breakfast cereals and beer.

From BBC • May 6, 2026

Spain's health ministry said on Tuesday the ship was due to arrive in the Canaries in "three to four days", adding that the island chain was the closest place with the necessary facilities.

From Barron's • May 6, 2026

It’s certainly a nice gesture, but not 100% necessary.

From MarketWatch • May 6, 2026

“ICE law enforcement officers are trained to use the minimum amount of force necessary to resolve dangerous situations to prioritize the safety of the public and our officers,” said Lauren Bis, a department spokesperson.

From Los Angeles Times • May 6, 2026

Irina was assigned to become an armorer, loading bombs and guns and doing necessary maintenance work.

From "A Thousand Sisters" by Elizabeth Wein

Related Words

• basic
• crucial
• decisive
• essential
• fundamental
• imperative
• indispensable
• mandatory
• needed
• paramount
• required
• significant
• unavoidable
• urgent
• vital