quantum

American  

[kwon-tuhm] / ˈkwɒn təm /

noun

• quanta
  plural

1. quantity or amount.

   the least quantum of evidence.

2. a particular amount.

3. a share or portion.

4. a large quantity; bulk.

5. Physics.

   1. the smallest quantity of radiant energy, equal to Planck's constant times the frequency of the associated radiation.

   2. the fundamental unit of a quantized physical magnitude, as angular momentum.

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adjective

1. sudden and significant.

   a quantum increase in productivity.

quantum British  

/ ˈkwɒntəm /

noun

1. physics

   1. the smallest quantity of some physical property, such as energy, that a system can possess according to the quantum theory

   2. a particle with such a unit of energy

2. amount or quantity, esp a specific amount

3. (often used with a negative) the least possible amount that can suffice

   there is not a quantum of evidence for your accusation

4. something that can be quantified or measured

5. (modifier) loosely, sudden, spectacular, or vitally important

   a quantum improvement

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quantum Scientific  

/ kwŏn′təm /

• quanta
  plural

1. A discrete, indivisible manifestation of a physical property, such as a force or angular momentum. Some quanta take the form of elementary particles; for example, the quantum of electromagnetic radiation is the photon, while the quanta of the weak force are the W and Z particles.

2. See also quantum state

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Other Word Forms

Derived Forms

• quantumness
  noun

Inflected Forms

Nouns

• quanta
  plural

Etymology

Origin of quantum

1610–20; noun use of neuter of Latin quantus how much

Explanation

While quantum refers to a general quantity or size, it is most often used in physics as a measure of the smallest amount of something — usually energy — that something can possess. The plural form is quanta. In the 17th century, the word quantum, from the Latin word for "how much," referred to a portion. Quantum is usually a noun referring to a specific amount of something. However, it can also be used as an adjective, as in the phrase "quantum leap," where it refers to a sudden, important change. Outside of physics, the word might be used with "not" to refer to something insignificant, as in "There's not a quantum of truth in what you say."

Example Sentences

See Examples For:

quantum quanta

Wright added, “Now when you start to look at quantum modeling, the reality of that becomes much more possible than it ever was before.”

From The Wall Street Journal ● Aug. 21, 2026

Secondly, the simulations themselves could become so complex that they might require more advanced computing resources, like yet-to-be-developed quantum machines.

From The Wall Street Journal ● Aug. 21, 2026

"Understanding how matter organizes itself under extreme quantum conditions gives us new tools for designing and controlling quantum systems. While this is fundamental research, discoveries like this often become the foundation for tomorrow's quantum technologies."

From Science Daily ● Aug. 21, 2026

ServiceNow’s Dave Wright breaks down the reality of the “SaaSpocalypse” and why businesses need to pay attention to quantum computing.

From The Wall Street Journal ● Aug. 21, 2026

Finally, in 1926, Heisenberg came up with a celebrated compromise, producing a new discipline that came to be known as quantum mechanics.

From "A Short History of Nearly Everything" by Bill Bryson

At wide-open throttle, the raunchiness doesn’t come in wild quanta but in one smoothly linear, incredibly steep exponential function, with no interval for tactility and feedback.

From The Wall Street Journal ● Oct. 30, 2025

The aim of the physicists in Düsseldorf was to measure the frequency of the required radiation quanta as precisely as possible and they achieved an unprecedented level of accuracy in their experiments.

From Science Daily ● Feb. 27, 2024

The analysis confirmed that both the input and output of the experiment were single quanta of energy.

From Scientific American ● Jun. 19, 2023

Quantum mechanics describes how, in the subatomic realm, everything is broken up in discrete chunks, or quanta, such as the individual particles of light called photons.

From New York Times ● May 8, 2023

In order to observe a primordial black hole one would have to detect several gamma ray quanta coming from the same direction within a reasonable space of time, such as a week.

From "A Brief History of Time: And Other Essays" by Stephen Hawking