: 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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Any scenario in which scalar-nucleon particles interact strongly with protons and neutrons would have cooled these stars far more than what telescopes actually see.
—
Rupendra Brahambhatt, Interesting Engineering, 6 Dec. 2025
But when a stream of solar protons hits, radiation levels on Earth's surface and around the planet suddenly spike.
—Tereza Pultarova, Space.com, 4 Dec. 2025
When the particles strike a proton inside the detector, a reaction triggers two light flashes that ping photomultiplier tubes and get converted into electrical signals.
—Jeanna Bryner, Scientific American, 26 Nov. 2025
The energy spectrum or range of gamma-ray emission intensities observed matches the emission predicted by the annihilation of theoretical dark matter particles, with a mass of around 500 times that of a proton, according to the researchers.
—Hannah Millington, MSNBC Newsweek, 25 Nov. 2025
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Rupendra Brahambhatt, Interesting Engineering, 6 Dec. 2025
But when a stream of solar protons hits, radiation levels on Earth's surface and around the planet suddenly spike.
—Tereza Pultarova, Space.com, 4 Dec. 2025
When the particles strike a proton inside the detector, a reaction triggers two light flashes that ping photomultiplier tubes and get converted into electrical signals.
—Jeanna Bryner, Scientific American, 26 Nov. 2025
The energy spectrum or range of gamma-ray emission intensities observed matches the emission predicted by the annihilation of theoretical dark matter particles, with a mass of around 500 times that of a proton, according to the researchers.
—Hannah Millington, MSNBC Newsweek, 25 Nov. 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 14 Dec. 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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