: 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 not only means dark matter is effectively invisible, but also that it can't be composed of particles like electrons, protons, and neutrons that make up the atoms that compose everyday matter like stars, planets, moons, and the cat next door.
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Robert Lea, Space.com, 17 June 2025
But the rest of the universe is made of cosmic baryons, or ordinary matter, which can be found in tiny particles called protons and neutrons.
—Ashley Strickland, CNN Money, 16 June 2025
As things cooled, quarks formed and then condensed into protons and neutrons.
—Philip Ball, Wired News, 8 June 2025
That includes atomic mass: lead has 82 protons in the nuclei of its atoms, while gold has 79.
—George Petras, USA Today, 17 May 2025
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Robert Lea, Space.com, 17 June 2025
But the rest of the universe is made of cosmic baryons, or ordinary matter, which can be found in tiny particles called protons and neutrons.
—Ashley Strickland, CNN Money, 16 June 2025
As things cooled, quarks formed and then condensed into protons and neutrons.
—Philip Ball, Wired News, 8 June 2025
That includes atomic mass: lead has 82 protons in the nuclei of its atoms, while gold has 79.
—George Petras, USA Today, 17 May 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 25 Jun. 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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