- (of a proposition) such that a denial of it involves a self-contradiction.
- (of an inference or argument) such that its conclusion cannot be false if its supporting premises are true.
- (of a condition) such that it must exist if a given event is to occur or a given thing is to exist.Compare sufficient(def 2).
noun, plural nec·es·sar·ies.
- necessary condition,
- necessary stool,
Origin of necessary
- (of a statement, formula, etc) true under all interpretations or in all possible circumstances
- (of a proposition) determined to be true by its meaning, so that its denial would be self-contradictory
- (of a property) essential, so that without it its subject would not be the entity it is
- (of an inference) always yielding a true conclusion when its premises are true; valid
- (of a condition) entailed by the truth of some statement or the obtaining of some state of affairsCompare sufficient (def. 2)
Word Origin for necessary
late 14c. "needed, required, essential, indispensable," from Old French necessaire "necessary, urgent, compelling" (13c.), and directly from Latin necessarius "unavoidable, indispensable, necessary," from necesse "unavoidable, indispensable," originally "no backing away," from ne- "not" + cedere "to withdraw, go away, yield" (see cede). The root sense is of that from which there is no evasion, that which is inevitable. Necessary house "privy" is from c.1600. Necessary evil is from 1540s (the original reference was to "woman").
mid-14c., "needed, required, or useful things; the necessities of life; actions determined by right or law," perhaps from Old French necessaire (n.) "private parts, genitalia; lavatory," and directly from Latin necessarius (n.), in classical Latin "a relation, relative, kinsman; friend, client, patron;" see necessary (adj.).