[ proh-ton ]

nounPhysics, Chemistry.
  1. a positively charged elementary particle that is a fundamental constituent of all atomic nuclei. It is the lightest and most stable baryon, having a charge equal in magnitude to that of the electron, a spin of ½, and a mass of 1.673 × 10-27 kg. Symbol: P

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Origin of proton

Term first suggested in 1920 by English physicist Ernest Rutherford as noun use of Greek prôton, neuter of prôtos “first,” the proton being the constituent of hydrogen nuclei, and formed on the analogy of electron; see first, electron

Other words from proton

  • pro·ton·ic, adjective

Words Nearby proton Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use proton in a sentence

British Dictionary definitions for proton


/ (ˈprəʊtɒn) /

  1. a stable, positively charged elementary particle, found in atomic nuclei in numbers equal to the atomic number of the element. It is a baryon with a charge of 1.602176462 × 10 –19 coulomb, a rest mass of 1.672 62159 × 10 –27 kilogram, and spin 1/2

Origin of proton

C20: from Greek prōtos first

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for proton


[ prōtŏn′ ]

  1. A stable subatomic particle in the baryon family having a mass of 1.672 X 10-24 grams (1,836 times that of the electron) and a positive electric charge of approximately 1.602 X 10-19 coulombs. Protons make up part of the nucleus of all atoms except hydrogen, whose nucleus consists of a single proton. In neutral atoms, the number of protons is the same as the number of electrons. In positively charged atoms, the number of protons is greater than the number of electrons, and in negatively charged atoms electrons outnumber protons. Protons are believed to be composed of two up quarks and one down quark. See Table at subatomic particle.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for proton


[ (proh-ton) ]

An elementary particle with a positive charge, found in the nucleus of an atom.

Notes for proton

A proton is over a thousand times heavier than an electron.

Notes for proton

Protons and neutrons make up most of an atom's mass.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.