: 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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In fact, humanity's discovery of subatomic particles other than electrons, protons, and neutrons, specifically positrons and muons came in 1933 via observations of cosmic rays.
—
Robert Lea, Space.com, 25 July 2025
Brian McNamara after receiving proton treatment for his rare cancer.
—Alyce Collins, MSNBC Newsweek, 20 July 2025
The two metals appear on the same line in the periodic table with their proton count and also their atomic number separated only by mercury (80) and thallium (81).
—Tim Treadgold, Forbes.com, 13 May 2025
Gaining a proton turns the nucleus into the next element on the periodic table.
—Jenna Ahart, Quanta Magazine, 2 July 2025
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Robert Lea, Space.com, 25 July 2025
Brian McNamara after receiving proton treatment for his rare cancer.
—Alyce Collins, MSNBC Newsweek, 20 July 2025
The two metals appear on the same line in the periodic table with their proton count and also their atomic number separated only by mercury (80) and thallium (81).
—Tim Treadgold, Forbes.com, 13 May 2025
Gaining a proton turns the nucleus into the next element on the periodic table.
—Jenna Ahart, Quanta Magazine, 2 July 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 29 Jul. 2025.
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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