proton

noun

pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: 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
protonic adjective

Examples of proton in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
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. 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

Word History

Etymology

Greek prōton, neuter of prōtos first — more at proto-

First Known Use

1920, in the meaning defined above

Time Traveler
The first known use of proton was in 1920

Browse Nearby Words

Cite this Entry

“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 25 Jun. 2025.

Kids Definition

proton

noun
pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: 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
protonic adjective

Medical Definition

proton

noun
pro·​ton ˈprō-ˌtän How to pronounce proton (audio)
: 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
protonic adjective

More from Merriam-Webster on proton

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