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noun, plural lep·ta [lep-tuh] /ˈlɛp tə/.
  1. an aluminum coin of modern Greece until the euro was adopted, the 100th part of a drachma.
  2. a small copper or bronze coin of ancient Greece.

Origin of lepton1

1715–25; < Greek leptón (nómisma) a small (coin), noun use of neuter of leptós small; see lepto-


noun Physics.
  1. any of a class of particles with spin of ½ that are not subject to the strong force and that are believed to be truly elementary and not composed of quarks or other subunits. The leptons known or believed to exist are the electron and electron-neutrino, the muon and mu-neutrino, and the tau lepton and tau-neutrino.

Origin of lepton2

1948; < Greek, neuter of leptós small, slight; see lepto-, -on1
Related formslep·ton·ic, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for lepton

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British Dictionary definitions for lepton


noun plural -ta (-tə)
  1. a former Greek monetary unit worth one hundredth of a drachma
  2. a small coin of ancient Greece

Word Origin

from Greek lepton (nomisma) small (coin)


  1. physics any of a group of elementary particles and their antiparticles, such as an electron, muon, or neutrino, that participate in electromagnetic and weak interactions and have a half-integral spin
Derived Formsleptonic, adjective

Word Origin

C20: from lepto- + -on
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

Word Origin and History for lepton


elementary particle of small mass, 1948, from Greek leptos "small, slight, slender, delicate" (from lepein "to peel," from PIE *lep-; see leper) + -on. Also the name of a small coin in ancient Greece, from neuter of leptos

Online Etymology Dictionary, © 2010 Douglas Harper

lepton in Medicine


  1. Any of a family of elementary particles that participate in the weak interaction, including the electron and its associated neutrino.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

lepton in Science


  1. Any of a family of elementary particles that interact through the weak force and do not participate in the strong force. Leptons include electrons, muons, tau particles, and their respective neutrinos, the electron neutrino, the muon neutrino, and the tau neutrino. The antiparticles of these six particles are also leptons. Compare hadron. See Note at elementary particle. See Table at subatomic particle.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

lepton in Culture



Any one of six elementary particles that are one of the fundamental constituents of matter. Leptons are not affected by the strong force and are not normally found in the nucleus of the atom. The electron and the neutrino are examples of leptons.

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.