Necessary or necessity may refer to:
Concept of necessity
- Need
- 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, something that is a required condition for something else to be the case
 - Necessary proposition, in logic, a statement about facts that is either unassailably true (tautology) or obviously false (contradiction)
 - Metaphysical necessity, in philosophy, a truth which is true in all possible worlds
 - Necessity in modal logic
 - Necessity good in economics
 
Law
- Doctrine of necessity, a concept in constitutional law
 - Military necessity, a concept in international law
 - Necessity (criminal law), a defence in criminal law
 - Necessity (tort), a concept in the law of tort
 - A necessity in contract law
 
Other uses
 Necessity., a poem by Letitia Elizabeth Landon being part of Three Extracts from the Diary of a Week, 1837.- "Necessary" (song), by Every Little Thing, 1998
 - A bathroom or toilet, 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
 - Necessity (novel), of 2016 by Jo Walton
 - Necessary Records, UK record label
 
See also
Wikiquote has quotations related to Necessary.
- All pages with titles beginning with Necessary
 - All pages with titles containing Necessary
 - All pages with titles beginning with necessity
 - All pages with titles containing necessity
 - Bare Necessities (disambiguation)
 
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