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

IonQ, Quantinuum, and other notable names in the quantum sector have reported earnings, which broadly showed that traction continues to grow.

From Barron's ● Aug. 15, 2026

In this system, however, the same quantum refrigerator can supply both heating and cooling.

From Science Daily ● Aug. 14, 2026

Many CEOs are still grappling with how to get meaningful value from AI, but a growing number have their sights set on the next potentially disruptive business technology: quantum computing.

From The Wall Street Journal ● Aug. 14, 2026

The researchers connected the transmon qubit to a quantum circuit refrigerator, allowing them to control heat flow on the quantum scale and demonstrate that this heat could be transformed into measurable work.

From Science Daily ● Aug. 14, 2026

We’d be able to explain to them everything we know—from the adventures of Alice in Wonderland to the paradoxes of quantum physics—and they could teach us how their people view the world.

From "Sapiens: A Brief History of Humankind" by Yuval Noah Harari

The challenge with Josephson junctions is that their behavior unfolds at the level of individual quanta.

From Science Daily ● Dec. 23, 2025

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

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

Sometimes the light quanta seemed to measure out at three or four meters long; sometimes they appeared to be “just a little bundle of energy,” Beams recalled.

From "Big Science" by Michael Hiltzik