The quality or state of being necessary, unavoidable, or absolutely requisite; inevitableness; indispensableness.

That which is necessary; a necessary; a requisite; something indispensable; -- often in the plural.

That which makes an act or an event unavoidable; irresistible force; overruling power; compulsion, physical or moral; fate; fatality.

The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism.

A state of affairs is necessary if it has to be the case. Logical necessity is a product of the law of noncontradiction. Causal necessity, it has been thought, is a different form of necessity.

A situation that compels an act because of some need; can provide grounds for an affirmative defense. See full article titled Defenses of Necessity and Choice of Lesser Evils

A person is excused from criminal liability where he acts in an emergency to protect life, health or property in a reasonable way and with no acceptable alternative. The law will excuse the commission of a lesser evil to avoid a greater evil when there are no other peaceful, effective alternative remedies open. The circumstances in which this defence might apply cannot be defined beforehand.

The whole of all physical and biological laws which govern the matter in every form and expression. liberty is the contrary.

Something that is necessary or required.

Something necessary or needed.

something that one must have

a need; something which cannot be avoided