: 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
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However, Chadwick said, the University of Kansas hospital plans to work with that hospital to provide specialized care, citing its radiation and proton therapy services for Children’s Mercy patients who need that care.
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Kendrick Calfee, Kansas City Star, 4 Apr. 2026
Electromagnetic radiation is strong, as the electromagnetic force between two protons is more than 30 orders of magnitude stronger than the gravitational force between those same two protons.
—Big Think, 3 Apr. 2026
Both of these decay rapidly into even more particles, so in the end, ultrahigh-energy protons (with more than 50 quintillion eV) from distant galaxies should never reach us.
—Phil Plait, Scientific American, 3 Apr. 2026
Deuterium has one proton and one neutron (as opposed to your regular old hydrogen, which has one proton and no neutrons).
—Keith Cooper, Space.com, 30 Mar. 2026
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Kendrick Calfee, Kansas City Star, 4 Apr. 2026
Electromagnetic radiation is strong, as the electromagnetic force between two protons is more than 30 orders of magnitude stronger than the gravitational force between those same two protons.
—Big Think, 3 Apr. 2026
Both of these decay rapidly into even more particles, so in the end, ultrahigh-energy protons (with more than 50 quintillion eV) from distant galaxies should never reach us.
—Phil Plait, Scientific American, 3 Apr. 2026
Deuterium has one proton and one neutron (as opposed to your regular old hydrogen, which has one proton and no neutrons).
—Keith Cooper, Space.com, 30 Mar. 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 8 Apr. 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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