: 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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To retrieve the energy, the researchers added an acid and a hydrogen-evolution catalyst to cause the electrons stored in the system to combine with protons, thereby releasing hydrogen.
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Ameya Paleja, Interesting Engineering, 27 Feb. 2026
Meanwhile, on the opposite side of the cell, the sulfate—a negative ion—moves towards the anode, where water is being split to produce protons and oxygen gas.
—IEEE Spectrum, 26 Feb. 2026
The proton was isolated in 1920, followed by the neutron in 1932.
—Big Think, 23 Feb. 2026
The result is that all the protons and electrons in the star are crushed into neutrons, and the mass of the incredibly dense object remains comparable to the sun, but the size is comparable to a city, as explained by NASA.
—Adam Harrington, CBS News, 9 Feb. 2026
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Ameya Paleja, Interesting Engineering, 27 Feb. 2026
Meanwhile, on the opposite side of the cell, the sulfate—a negative ion—moves towards the anode, where water is being split to produce protons and oxygen gas.
—IEEE Spectrum, 26 Feb. 2026
The proton was isolated in 1920, followed by the neutron in 1932.
—Big Think, 23 Feb. 2026
The result is that all the protons and electrons in the star are crushed into neutrons, and the mass of the incredibly dense object remains comparable to the sun, but the size is comparable to a city, as explained by NASA.
—Adam Harrington, CBS News, 9 Feb. 2026
See All Example Sentences for proton
Cite this Entry
“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 6 Mar. 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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