adjective 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 ... dictionary.reference.com
Definition of NECESSARY. 1. a: of an inevitable nature : inescapable b (1): logically unavoidable (2): that cannot be denied without contradiction c: determined or ... www.merriam-webster.com
Necessary or necessity may refer to: 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 ... en.wikipedia.org
necessary (n s-s r) adj. 1. Absolutely essential. See Synonyms at indispensable. 2. Needed to achieve a certain result or effect; requisite: the necessary tools. www.thefreedictionary.com