Definition of "quantum"

quantum

/ˈkwɒntəm/

noun
countable and uncountable, plural quantums or quanta
1. (now chiefly South Asia or law) The total amount of something; quantity.
  Quotations
  The reader will perhaps be curious to know the quantum of this present, but we cannot satisfy his curiosity.
  1749, Henry Fielding, Tom Jones, Folio Society, published 1973, page 416
  A certain quantum of power must always exist in the community, in some hands, and under some appellation.
  1790, Edmund Burke, Reflections on the Revolution in France, Oxford, published 2009, page 142
  Otherwise I will have given the lie to my maxim that whether you work eight or twenty hours, the quantum of work that gets done on a normal day is the same.
  1997, Kiran Nagarkar, Cuckold, HarperCollins, published 2013, page 375
  The Congress's core ministerial panel on Friday gave its green signal to raising motor fuel prices but the quantum of increase emerged as a hitch.
  2008 May 21, The Times of India
  1. (law) The amount of compensation awarded to a successful party in a lawsuit.
  2. (law) The length or magnitude of the sentence handed down to someone who has been found guilty of a crime.
2. The amount or quantity observably present, or available.
  Quotations
  Each man has only a quantum of compassion, he argued, and mine is used up for the day.
  1979, John Le Carré, Smiley's People, Folio Society, published 2010, page 96
  The dream of flying, according to Strümpell, is the appropriate image used by the psyche to interpret the quantum of stimulus [translating Reizquantum] proceeding from the rise and fall of the lungs when the cutaneous sensation of the thorax has simultaneously sunk into unconsciousness.
  1999, Sigmund Freud, translated by Joyce Crick, The Interpretation of Dreams, Oxford, published 2008, page 34
3. (physics) The smallest possible, and therefore indivisible, unit of a given quantity or quantifiable phenomenon.
  Quotations
  The quantum of light energy was later called a photon.
  2002, David C Cassidy et al., Understanding Physics, Birkhauser 2002, p. 602
4. (computing) The amount of time allocated for a thread to perform its work in a multithreaded environment.
5. (computing, uncountable) Short for quantum computing.
6. (medicine) The minimum dose of a pathogen required to cause an infection.
7. (mathematics) A definite portion of a manifoldness, limited by a mark or by a boundary.
  Quotations
  Defined parts of a manifoldness are called Quanta
  1882, William Kingdon Clifford, Mathematical Papers
adjective
not comparable
1. Of a change, sudden or discrete, without intermediate stages.
2. (informal) Of a change, significant.
3. (physics) Involving quanta, quantum mechanics or other aspects of quantum physics.
  Quotations
  Some of the most beautiful and thus appealing physical theories, including quantum electrodynamics and quantum gravity, have been dogged for decades by infinities that erupt when theorists try to prod their calculations into new domains. Getting rid of these nagging infinities has probably occupied far more effort than was spent in originating the theories.
  2012 January, Michael Riordan, “Tackling Infinity”, in American Scientist‎, volume 100, number 1, archived from the original on 19 June 2017, page 86
  1. (computing theory) Relating to a quantum computer.