necessary

Definitions

Required to be done, achieved, or present; essential.

Determined, existing, or happening by natural laws or inevitable necessity; unavoidable.

Examples

It is necessary to arrive at the airport two hours before your flight.

Water is necessary for the survival of all living organisms.

Synonyms

essential required vital compulsory mandatory indispensable requisite

Antonyms

unnecessary optional dispensable nonessential needless superfluous gratuitous