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

Inflected Forms

noun

• 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

Their new theoretical method can generate and control a wide range of entangled quantum states using tools that are already common in many quantum physics laboratories.

From Science Daily • Jun. 6, 2026

In theory, entangled quantum states can detect extremely small differences in magnetic fields or gravitational fields between separate locations.

From Science Daily • Jun. 6, 2026

The discovery suggests that our understanding of ferromagnetic metals remains incomplete and reveals new opportunities for research into magnetism, topological matter, and the unusual excitations that emerge from these quantum states.

From Science Daily • Jun. 5, 2026

At first, Quantinuum seemed to be launching into a market gripped by quantum fever.

From Barron's • Jun. 5, 2026

Perhaps the weirdest of all is caused by a zero in the equations of quantum mechanics: the zero-point energy.

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