necessary: Meaning and Definition of

nec•es•sar•y

1. being essential, indispensable, or requisite: a necessary part of the motor.
2. happening or existing by necessity: a necessary change in our plans.
3. acting or proceeding from compulsion or necessity; not free; involuntary: a necessary agent.
1. (of a proposition) such that a denial of it involves a self-contradiction.
2. (of an inference or argument) such that its conclusion cannot be false if its supporting premises are true.
3. (of a condition) such that it must exist if a given event is to occur or a given thing is to exist. Cf.sufficient(def. 2).

1. something necessary or requisite; necessity.
2. food, clothing, etc., required by a dependent or incompetent and varying with his or her social or economic position or that of the person upon whom he or she is dependent.
3. a privy or toilet.