Necessary may refer to: Something that's a required condition for something else to be the case, see necessary and sufficient condition. A necessary truth, something that can't fail to be true, see logical possibility. An important task or essential thing to do at a particular time or by a particular moment. Necessity in the context of criminal law An action somebody may feel they must do In some languages a "necessary"'s a bathroom or toilet. In English this's an archaic usage.… (More on Necessary)