Necessary or necessity may refer to:

Concept of necessity

Need A need is a deficiency 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 kind of logic used to represent statements about necessity and possibility. In philosophy and related fields it is used as a tool for understanding concepts such as knowledge, obligation, and causation. For instance, in epistemi ...

, 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 Modal logic is a kind of logic used to represent statements about Modality (natural language), necessity and possibility. In philosophy and related fields it is used as a tool for understanding concepts such as knowledge, obligation, and causality ...

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 i ...

in economics

Law

Doctrine of necessity The doctrine of necessity is the basis on which extraordinary actions by administrative authority, which are designed to restore order or uphold fundamental constitutional principles, are considered to be lawful even if such an action contravenes ...

, a concept in constitutional law *

Military necessity Military necessity, along with distinction (law), distinction, and proportionality (international humanitarian law), proportionality, are three important principles of international humanitarian law governing the laws of war, legal use of force i ...

, 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 b ...

, 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, t ...

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

contract law A contract is an agreement that specifies certain legally enforceable rights and obligations pertaining to two or more Party (law), parties. A contract typically involves consent to transfer of goods, Service (economics), services, money, or pr ...

Other uses

* , 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. Landon's writings are emblematic of the transition from Romanticism to Victorian literature. Her first major b ...

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

bathroom A bathroom is a room in which people wash their bodies or parts thereof. It can contain one or more of the following plumbing fixtures: a shower, a bathtub, a bidet, and a sink (also known as a wash basin in the United Kingdom). A toilet is al ...

toilet A toilet is a piece of sanitary hardware that collects human waste (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 p ...

, 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

Concept of necessity

Law

Other uses

See also