Definition of "necessity"

necessity

/nɪˈsɛsəti/

noun
countable and uncountable, plural necessities
1. The quality or state of being necessary, unavoidable, or absolutely requisite.
  Quotations
  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 June 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.
  Quotations
  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.
  1863, Richard Sibbes, The Successful Seeker, in The Complete Works of Richard Sibbes, D.D., Volume VI, James Nichol, page 125
3. Something necessary; a requisite; something indispensable.
  Quotations
  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.
  Quotations
  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.
7. (law, in the plural) Indispensable requirements (of life).