Necessary or necessity may refer to: *

Need A need is dissatisfaction at a point of time and in a given context. Needs are distinguished from wants. In the case of a need, a deficiency causes a clear adverse outcome: a dysfunction or death. In other words, a need is something required for a ...

** An action somebody may feel they must do ** An important task or essential thing to do at a particular time or by a particular moment *

Necessary and sufficient condition In logic and mathematics, necessity and sufficiency are terms used to describe a conditional or implicational relationship between two statements. For example, in the conditional statement: "If then ", is necessary for , because the truth of ...

, in logic, something that is a required condition for something else to be the case *

Necessary proposition Modal logic is a collection of formal systems developed to represent statements about necessity and possibility. It plays a major role in philosophy of language, epistemology, metaphysics, and natural language semantics. Modal logics extend other ...

, in logic, a statement about facts that is either unassailably true (tautology) or obviously false (contradiction) *

Metaphysical necessity In philosophy, metaphysical necessity, sometimes called broad logical necessity, is one of many different kinds of necessity, which sits between logical necessity and nomological (or physical) necessity, in the sense that logical necessity entails ...

, in philosophy, a truth which is true in all possible worlds * Necessity in modal logic *

Necessity good In economics, a necessity good or a necessary good is a type of normal good. Necessity goods are product(s) and services that consumers will buy regardless of the changes in their income levels, therefore making these products less sensitive to inc ...

in economics ;Law *

Doctrine of necessity The doctrine of necessity is the basis on which extra-constitutional actions by administrative authority, which are designed to restore order or attain power on the pretext of stability, are considered to be lawful even if such an action contrave ...

, a concept in constitutional law *

Military necessity Military necessity, along with distinction, and proportionality, are three important principles of international humanitarian law governing the legal use of force in an armed conflict. Attacks Military necessity is governed by several constra ...

, a concept in international law *

Necessity (criminal law) In the criminal law of many nations, necessity may be either a possible justification or an exculpation for breaking the law. Defendants seeking to rely on this defense argue that they should not be held liable for their actions as a crime ...

, a defence in criminal law *

Necessity (tort) In tort common law, the defense of necessity gives the state or an individual a privilege to take or use the property of another. A defendant typically invokes the defense of necessity only against the intentional torts of trespass to chattels, ...

, a concept in the law of tort * A necessity in

contract law A contract is a legally enforceable agreement between two or more parties that creates, defines, and governs mutual rights and obligations between them. A contract typically involves the transfer of goods, services, money, or a promise to tran ...

;Other * , a poem by

Letitia Elizabeth Landon Letitia Elizabeth Landon (14 August 1802 – 15 October 1838) was an English poet and novelist, better known by her initials L.E.L. The writings of Landon are transitional between Romanticism and the Victorian Age. Her first major breakthrough ...

being part of ''Three Extracts from the Diary of a Week'', 1837. * "Necessary" (song), by Every Little Thing, 1998 * A

bathroom A bathroom or washroom is a room, typically in a home or other residential building, that contains either a bathtub or a shower (or both). The inclusion of a wash basin is common. In some parts of the world e.g. India, a toilet is typically ...

toilet A toilet is a piece of sanitary hardware that collects human urine and feces, and sometimes toilet paper, usually for disposal. Flush toilets use water, while dry or non-flush toilets do not. They can be designed for a sitting position popu ...

, in some languages (in English this is an archaic usage) * An economic need enunciated by US President Franklin D. Roosevelt in his 1944

Second Bill of Rights The Second Bill of Rights or Bill of Economic Rights was proposed by United States President Franklin D. Roosevelt during his State of the Union Address on Tuesday, January 11, 1944. In his address, Roosevelt suggested that the nation had come ...

* ''Necessity'' (novel), of 2016 by Jo Walton * Necessary Records, UK record label

See also