proton Hear it!

proton definition

pro·ton (prō′tän′)

noun

Particle Physics a nucleon carrying a positive charge equal to the negative charge of an electron and having a mass of c. 1.673 × 10kg (c. 938.2796 MeV/c, c. 1,836 times the mass of an electron): the number of protons in an atom determines the atomic number of a chemical element

Etymology: ModL < Gr prōton, neut. of prōtos, first: see proto-

Webster's New World College Dictionary Copyright © 2009 by Wiley Publishing, Inc., Cleveland, Ohio.
Used by arrangement with John Wiley & Sons, Inc.

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