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

While other tech giants spend on AI data centers, Big Blue aims to keep selling mainframes and pour profits into quantum computing.

From The Wall Street Journal ● Jul. 24, 2026

On Thursday, it announced it will acquire HRL Laboratories, which brings in complementary research on the fundamental units of quantum computing, called qubits.

From The Wall Street Journal ● Jul. 23, 2026

When it comes to the total size of the opportunity for quantum computing, “I have actually upped my estimate,” says Krishna.

From The Wall Street Journal ● Jul. 23, 2026

The findings show that quantum effects can be used to control charge and energy transfer in complex materials even at room temperature.

From Science Daily ● Jul. 22, 2026

Zero in quantum mechanics invests the vacuum with infinite energy.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife

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

Photons are "light quanta" that constitute the basic building blocks making up the electromagnetic radiation field.

From Science Daily ● Mar. 6, 2024

Quantum theory typically deals with the universe in tiny chunks, or quanta, while general relativity takes the cosmos to be continuous even at the smallest scales.

From Scientific American ● Aug. 19, 2023

General relativity does not contain any notion of quanta; a quantum theory of gravity is an ambition that remains unfinished today.

From New York Times ● May 8, 2023

They vibrate only with certain acceptable energies, called quanta.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife