quan·​tum | \ ˈkwän-təm How to pronounce quantum (audio) \
plural quanta\ ˈkwän-​tə How to pronounce quantum (audio) \

Definition of quantum

 (Entry 1 of 2)

b : portion, part
c : gross quantity : bulk
2a : any of the very small increments or parcels into which many forms of energy are subdivided
b : any of the small subdivisions of a quantized physical magnitude (such as magnetic moment)



Definition of quantum (Entry 2 of 2)

1 : large, significant a quantum improvement
2 : of, relating to, or employing the principles of quantum mechanics quantum physics

Keep scrolling for more

Synonyms for quantum

Synonyms: Noun

Visit the Thesaurus for More 

Examples of quantum in a Sentence

Noun the sum of human knowledge is now so immense that even a highly educated person can hope to absorb only a tiny quantum of it
Recent Examples on the Web: Noun Third, how a potential quantum computer neural simulation is set up might be able to take advantage of the physics the brain is subject to. Gabriel A. Silva, Forbes, 3 Sep. 2021 Physicists like Nobel laureate Frank Wilczek are trying to figure out how to make a practical topological quantum computer on Earth. Stephon Alexander, Wired, 31 Aug. 2021 In 2019, Google announced that its Sycamore quantum computer had completed a task in 200 seconds that would take a conventional computer 10,000 years. Quanta Magazine, 2 Aug. 2021 First, neither quantum computer can do anything useful. Daniel Garisto, Scientific American, 15 July 2021 So far, no scalable, commercial-grade quantum computer has been built. Sara Castellanos, WSJ, 8 June 2021 In the lab, Schöllhorn’s team calculated each nest’s quantum yield, or its capacity to emit light when fed a certain number of photons. Katherine J. Wu, The Atlantic, 24 Aug. 2021 Put another way, observing a quantum system fundamentally changes the system. Courtney Linder, Popular Mechanics, 23 Aug. 2021 After all, there’s no such job as a quantum mechanic. Rhett Allain, Wired, 20 Aug. 2021 Recent Examples on the Web: Adjective Helps Ultracold Quantum Experiments Go Small Cutting-edge devices used for quantum experiments have been bulky, finicky, and confined to academic labs—so far. Karmela Padavic-callaghan, Wired, 7 Sep. 2021 This is where time crystals also offer even more promise than quantum qubit computing alone. Caroline Delbert, Popular Mechanics, 4 Aug. 2021 Scientists from around the world claim to have harnessed a time crystal inside a quantum computer. Caroline Delbert, Popular Mechanics, 4 Aug. 2021 The new time crystal demo marks one of the first times a quantum computer has found gainful employment. Quanta Magazine, 2 Aug. 2021 The startup, co-founded by Shahar Keinan and Bill Shipman, came out of stealth a year ago, revealing the first-ever drug discovery platform using a quantum computer, cost-efficiently scanning billions of molecules from a large chemical space. Gil Press, Forbes, 25 June 2021 And even with compression, longer baselines would still warrant quantum repeaters. Anil Ananthaswamy, Scientific American, 19 Apr. 2021 Time crystals might introduce a better method for sustaining quantum computing, according to Yao, who published a blueprint for making time crystals in 2017. Washington Post, 12 Aug. 2021 Wigner crystal melting is a quantum phase transition — one that is similar to an ice cube becoming water, but without any heating involved. Quanta Magazine, 12 Aug. 2021

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'quantum.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of quantum


1567, in the meaning defined at sense 1a


1942, in the meaning defined at sense 1

History and Etymology for quantum


Latin, neuter of quantus how much

Keep scrolling for more

Learn More About quantum

Time Traveler for quantum

Time Traveler

The first known use of quantum was in 1567

See more words from the same year

Dictionary Entries Near quantum



quantum chromodynamics

See More Nearby Entries 

Statistics for quantum

Last Updated

11 Sep 2021

Cite this Entry

“Quantum.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/quantum. Accessed 21 Sep. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for quantum



English Language Learners Definition of quantum

 (Entry 1 of 2)

: the smallest amount of many forms of energy (such as light)



English Language Learners Definition of quantum (Entry 2 of 2)

: of, relating to, or using the principles of quantum theory


quan·​tum | \ ˈkwänt-əm How to pronounce quantum (audio) \
plural quanta\ ˈkwänt-​ə How to pronounce quantum (audio) \

Medical Definition of quantum

1 : one of the very small increments or parcels into which many forms of energy are subdivided a molecule of rhodopsin in the human eye can cause a response to a single quantum of light
2 : one of the small molecular packets of a neurotransmitter (as acetylcholine) released into the synaptic cleft in the transmission of a nerve impulse across a synapse

More from Merriam-Webster on quantum

Nglish: Translation of quantum for Spanish Speakers

Britannica English: Translation of quantum for Arabic Speakers

Britannica.com: Encyclopedia article about quantum


Test Your Vocabulary

Difficult Spelling Words Quiz

  • alphabet pasta spelling help
  • Which is the correct spelling?
Spell It

Can you spell these 10 commonly misspelled words?


Anagram puzzles meet word search.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!