necessity

Etymology

From Middle English necessite, from Old French necessite, from Latin necessitās (“unavoidableness, compulsion, exigency, necessity”), from necesse (“unavoidable, inevitable”); see necessary.

noun

1. The quality or state of being necessary, unavoidable, or absolutely requisite.
   I bought a new table out of necessity. My old one was ruined.
   Seeing the British establishment struggle with the financial sector is like watching an alcoholic […]. Until 2008 there was denial over what finance had become. […] But the scandals kept coming, […]. A broad section of the political class now recognises the need for change but remains unable to see the necessity of a fundamental overhaul. 2013-06-28, Joris Luyendijk, “Our banks are out of control”, in The Guardian Weekly, volume 189, number 3, page 21
2. The condition of being needy; desperate need; lack.
   1863, Richard Sibbes, The Successful Seeker, in The Complete Works of Richard Sibbes, D.D., Volume VI, James Nichol, page 125, For it is in vain for a man to think to seek God in his necessity and exigence, if he seek not God in his ordinances, and do not joy in them.
3. Something necessary; a requisite; something indispensable.
   A tent is a necessity if you plan on camping.
   Look for the bare necessities / The simple bare necessities / Forget about your worries and your strife 1967, Terry Gilkyson (lyrics and music), “The Bare Necessities”, in The Jungle Book
   Love and compassion are necessities, not luxuries. Without them humanity cannot survive. 20th century, Tenzin Gyatso (attributed)
4. Something which makes an act or an event unavoidable; an irresistible force; overruling power.
   After eating a full meal, the human body's necessity for food will compel the person to eat again in the future.
   I stopped, and said with inly muttered voice, 'It doth not love the shower, nor seek the cold: This neither is its courage nor its choice, But its necessity in being old. 1804, The Small Celandine, Wordsworth
5. The negation of freedom in voluntary action; the subjection of all phenomena, whether material or spiritual, to inevitable causation; necessitarianism.
6. (law) Greater utilitarian good; used in justification of a criminal act.
   doctrine of necessity
7. (law, in the plural) Indispensable requirements (of life).