from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A quantity or amount.
  • n. A specified portion.
  • n. Something that can be counted or measured.
  • n. Physics The smallest amount of a physical quantity that can exist independently, especially a discrete quantity of electromagnetic radiation.
  • n. Physics This amount of energy regarded as a unit.
  • adj. Relating to or based upon quantum mechanics.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Of a change, sudden or discrete, without intermediate stages.
  • adj. Of a change, significant.
  • adj. Involving quanta
  • adj. Relating to a quantum computer

from the GNU version of the Collaborative International Dictionary of English

  • n. Quantity; amount.
  • n. A definite portion of a manifoldness, limited by a mark or by a boundary.

from The Century Dictionary and Cyclopedia

  • n. That which has quantity; a concrete quantity.
  • n. A prescribed, proper, or sufficient amount.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a discrete amount of something that is analogous to the quantities in quantum theory
  • n. (physics) the smallest discrete quantity of some physical property that a system can possess (according to quantum theory)


from The American Heritage® Dictionary of the English Language, 4th Edition

Latin, from neuter of quantus, how great; see quantity.

from Wiktionary, Creative Commons Attribution/Share-Alike License

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


  • ~ Hidden order found in a quantum spin liquid -- An international team, including scientists from the London Centre for Nanotechnology, has detected a hidden magnetic “quantum order” that extends over chains of 100 atoms in a ceramic without classical magnetism.

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  • The word quantum is thrown around a lot these days in media like in the film What the Bleep Do We Know?

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  • In 1902, two years after the physicist Max Planck first coined the term quantum to describe the core reality of light, a young British writer named James Allen penned a little book entitled As a Man Thinketh, which drew its title and its message from the biblical verse “As a man thinketh in his heart, so is he.”

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  • While the word quantum is now used as an exotic adjective to augment the sales of everything from diets to fishing tackle, the connection proposed here is not trivial.


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  • Satar is ready to make what he calls a quantum leap.

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  • And Jane, I want to say to anybody out there who wants to change their life by changing their thinking and getting rid of those patterns, I ` ve got a free what I call quantum thinking lesson on my Web site: DocWade. com.

    CNN Transcript Mar 30, 2009

  • WOLF: The mind is a process, and it's related to what is happening at the level of what we call the quantum field of reality.

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  • I have discovered in my research with consumers what I call the quantum theory of shopping, which in one simple equation, that even the mathematically challenged can understand, explains all shopping behavior.

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  • At least, what they called quantum physics back then, even though they had no idea that—



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  • I'm not so sure that 'quantum leap' is obviously misused. The word 'quantum' can be used of any measurable quantity--and this use far predates the physicists' adoption of the word for the smallest measurable quantity--and by this use, to call something a quantum x is like calling it a sizable x. Interestingly, we also typically hear 'ABC is a sizable x' to mean that ABC is a large x. Perhaps something like this explains how the phrase 'quantum leap' came to mean what it evidently does mean, despite the technical meaning of 'quantum' in physics.

    November 26, 2009

  • Thanks for the explanation, all! I suspect people will keep on using "quantum leap" to mean a significant, world-altering change, and physicists will keep arguing over whether such popular use is valid. Unfortunately, people like cliches, and more to the point, we love cliches that make us sound smart.

    December 22, 2008

  • The problem with "quantum leap" is not that people misunderstand it, but that it's a cliche.

    A common example of a quantum leap is an electron changing orbital levels around an atom. The change results in different chemical properties of the atom, so a quantum leap is small but significant. "Quantum leap" as opposed to "quantum step" can also imply that the electron has by-passed a couple of orbital levels.

    I think it's a valid analogy to speak of a quantum leap in understanding. It means that someone has reached a new level, that things have gelled. One might have little new knowledge, but suddenly see how to apply their knowledge.

    December 21, 2008

  • Alas yes. Rather like decimate, quantum and "quantum leap/change" can't really be used precisely in everyday language. Best to leave it to the scientists, and confine it to the bin of corporate weasel words elsewhere

    December 21, 2008

  • rolig: that's exactly right. A point at the center of my slightly over-the-top review here:

    Review of "Why Things Fail"

    The relevant point is in the material pertaining to chapter 5, if you make it that far. The author had some point to make about how people misuse the term "quantum change", but his discussion just added to the confusion.

    I think that it is what the inestimable Bryan Garner would refer to as a "skunked term" - one which carries with it an inescapable aura of confusion (when used in anything other than its narrow, specialized sense)

    December 21, 2008

  • So wouldn't this mean that a "quantum leap" was minimal change, and not the huge change we usually want this phrase to mean?

    December 21, 2008

  • That is the perfect definition of quantum, William. Thank you for your wonderful contribution!

    December 21, 2008

  • quantum (n):the minimum amount a system can change; e.g., a photon is the minimum amount in electrodynamics;

    December 21, 2008