proton

noun

pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: an elementary particle that is identical with the nucleus of the hydrogen atom, that along with the neutron is a constituent of all other atomic nuclei, that carries a positive charge numerically equal to the charge of an electron, and that has a mass of 1.673 × 10−27 kilogram
protonic
prō-ˈtä-nik How to pronounce proton (audio)
adjective

Examples of proton in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Neutrinos are produced when other particles, such as protons, collide with particles of light, or photons, or with different sorts of matter. — Robert Lea, Space.com, 6 July 2026 But when the new proton device was operational this month, the team incorporated that into De La Torre’s plan. — Grant Stringer, Mercury News, 18 June 2026 The strategy process evaluated a wide range of proposals, including linear electron-positron colliders, muon colliders, electron-proton facilities, and reuse of the existing LHC tunnel. — Florencia Canelli, Scientific American, 1 July 2026 For the project, scientists at the Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Baden-Württemberg, directly coupled concentrating photovoltaic cells with proton exchange membrane (PEM) electrolyzer cells. — Georgina Jedikovska, Interesting Engineering, 29 June 2026 See All Example Sentences for proton

Word History

Etymology

Greek prōton, neuter of prōtos first — more at proto-

First Known Use

1920, in the meaning defined above

Time Traveler
The first known use of proton was in 1920

Phrases Containing proton

Rhymes for proton

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Browse Nearby Words

Protomycetales
proton
protonate
See all Nearby Words

Cite this Entry

“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 7 Jul. 2026.

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Kids Definition

proton

noun
pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: an atomic particle that occurs in the nucleus of every atom and carries a positive charge equal in size to the negative charge of an electron
protonic
prō-ˈtän-ik How to pronounce proton (audio)
adjective

Medical Definition

proton

noun
pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: an elementary particle that is identical with the nucleus of the hydrogen atom, that along with neutrons is a constituent of all other atomic nuclei, that carries a positive charge numerically equal to the charge of an electron, and that has a mass of 1.673×10−24 gram
protonic
prō-ˈtän-ik How to pronounce proton (audio)
adjective

More from Merriam-Webster on proton

Nglish: Translation of proton for Spanish Speakers

Britannica.com: Encyclopedia article about proton

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