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

Necessity n. : The condition of being needy or necessitous; pressing need; indigence; want.

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

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

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

Example:
How has Computer networks have become a Necessity for most businesses?

Taxonomy
defense, defendant, law, safe from harm, actor, defense of justification, breaking the law, provisions, belief, physical force, circumstances, defence, the accused, United States, defence of necessity, free encyclopedia, element, evils.

Defination from the web:
necessity defense will not be recognized if the defendant drove further than was ... lack the financial means to feed their children cannot use necessity as a defense if they steal food. ... Main article: Necessity in English law ...