Definition of necessity

• n. - The quality or state of being necessary, unavoidable, or absolutely requisite; inevitableness; indispensableness.
• n. - The condition of being needy or necessitous; pressing need; indigence; want.
• n. - That which is necessary; a necessary; a requisite; something indispensable; -- often in the plural.
• n. - That which makes an act or an event unavoidable; irresistible force; overruling power; compulsion, physical or moral; fate; fatality.
• n. - The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism.