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.
First, scientists will measure stability boundaries to find out how many protons and neutrons a single nucleus can contain before breaking apart. — Aman Tripathi, Interesting Engineering, 1 Aug. 2026 That force tightly binds particles known as quarks into composite particles such as protons and neutrons. — Matt Von Hippel, Quanta Magazine, 29 July 2026 Miller had been building one of the massive, intricate cameras needed to detect the Higgs boson created by colliding protons. — Lisa Song, CNN Money, 28 July 2026 The remnant’s northern part is aglow with gamma rays from accelerated protons, however—indicating the shock is interacting with a dense cloud of ionized hydrogen gas called the S249 H II region. — Damien Pine, Scientific American, 21 July 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

See All Rhymes for proton

Browse Nearby Words

Protomycetales
proton
protonate
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Cite this Entry

“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 5 Aug. 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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