: 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
Examples of proton in a Sentence
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This has led scientists to suggest a whole host of hypothetical particles to account for dark matter, which go beyond the standard model of particle physics and the electrons, protons and neutrons that make up the atoms that compose all everyday matter, like stars, planets, moons and our bodies.
—
Robert Lea, Space.com, 9 Jan. 2026
Acidic moisture increased voltage significantly, as protons act as efficient charge carriers.
—Prabhat Ranjan Mishra, Interesting Engineering, 5 Jan. 2026
Electrons have positrons, which are anti-electrons, while protons have antiprotons.
—Dipangkar Dutta, The Conversation, 15 Dec. 2025
The state Public Health Council on Wednesday unanimously approved UMass Memorial Health Care’s application to buy a proton beam, and expand UMass Memorial’s Cancer Center at Marlborough Hospital in order to offer proton therapy services.
—Boston Herald Wire Services, Boston Herald, 10 Dec. 2025
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Robert Lea, Space.com, 9 Jan. 2026
Acidic moisture increased voltage significantly, as protons act as efficient charge carriers.
—Prabhat Ranjan Mishra, Interesting Engineering, 5 Jan. 2026
Electrons have positrons, which are anti-electrons, while protons have antiprotons.
—Dipangkar Dutta, The Conversation, 15 Dec. 2025
The state Public Health Council on Wednesday unanimously approved UMass Memorial Health Care’s application to buy a proton beam, and expand UMass Memorial’s Cancer Center at Marlborough Hospital in order to offer proton therapy services.
—Boston Herald Wire Services, Boston Herald, 10 Dec. 2025
See All Example Sentences for proton
Cite this Entry
“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 19 Jan. 2026.
Copy CitationKids Definition
proton
noun
pro·ton
ˈprō-ˌtän 
: 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
Medical Definition
proton
noun
pro·ton
ˈprō-ˌtän
: 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
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