: 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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Deuterated water refers to water in which one hydrogen atom is replaced with deuterium, a heavy hydrogen isotope that has an atomic nucleus composed of one proton and one neutron.
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Robert Lea, Space.com, 23 Apr. 2026
In fact, the record-setting collider prior to the LHC, the Tevatron at Fermilab, used to make antiproton beams that would collide with protons in their accelerator, leading to incredible fundamental discoveries in the late 20th century, including the top quark.
—Big Think, 22 Apr. 2026
As protons are pumped out, thousands more flow in, drawn by the net negative electric charge and the general tendency for entropy to rise as particles (in this case, protons) spread out in space ever more evenly.
—Quanta Magazine, 20 Apr. 2026
The combined fuzziness of the electron and proton means that the electron can be anywhere inside that region—including inside the proton.
—ArsTechnica, 14 Apr. 2026
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Robert Lea, Space.com, 23 Apr. 2026
In fact, the record-setting collider prior to the LHC, the Tevatron at Fermilab, used to make antiproton beams that would collide with protons in their accelerator, leading to incredible fundamental discoveries in the late 20th century, including the top quark.
—Big Think, 22 Apr. 2026
As protons are pumped out, thousands more flow in, drawn by the net negative electric charge and the general tendency for entropy to rise as particles (in this case, protons) spread out in space ever more evenly.
—Quanta Magazine, 20 Apr. 2026
The combined fuzziness of the electron and proton means that the electron can be anywhere inside that region—including inside the proton.
—ArsTechnica, 14 Apr. 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 28 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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