quantum

Definition of quantum

Etymology

From Late Latin quantum, noun use of neuter form of Latin quantus (“how much”).

Pronunciation

• (UK) IPA: /ˈkw�'ntəm/
• (US) IPA: /ˈkwɑn(t)əm/
• SAMPA: /"kwan.t@m/

Noun

quantum (plural quanta)

1. (now chiefly South Asia) The total amount of something; quantity. [from 17th c.]
   
   * 1749, Henry Fielding, Tom Jones, Folio Society 1973, p. 416:
   The reader will perhaps be curious to know the quantum of this present, but we cannot satisfy his curiosity.
   
   * 2008, The Times of India, 21 May 2008:
   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.
   
   
2. The amount or quantity observably present, or available. [from 18th c.]
   
   * 1999, Joyce Crick, translating Sigmund Freud, The Interpretation of Dreams, Oxford 2008, p. 34:
   The dream of flying, according to Strümpell, is the appropriate image used by the psyche to interpret the quantum of stimulus [transl. Reizquantum] proceeding from the rise and fall of the lungs when the cutaneous sensation of the thorax has simultaneously sunk into unconsciousness.
   
   
3. (physics) The smallest possible, and therefore indivisible, unit of a given quantity or quantifiable phenomenon. [from 20th c.]
   
   * 2002, David C Cassidy et al., Understanding Physics, Birkhauser 2002, p. 602:
   The quantum of light energy was later called a photon.

Adjective

quantum (not comparable)

1. (informal) Of a change, significant
2. (physics) Involving quanta