necessity

n.

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