Dictionary.com
definitions
  • synonyms

photon

[foh-ton]
noun
  1. a quantum of electromagnetic radiation, usually considered as an elementary particle that is its own antiparticle and that has zero rest mass and charge and a spin of one. Symbol: γ
Show More

Origin of photon

First recorded in 1900–05; phot- + -on1
Also called light quantum.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for photon

Contemporary Examples

Historical Examples

  • Or, the photon may be retained for a while and emitted again relatively unchanged—the effect observed in luminous paint.

    The Mercenaries

    Henry Beam Piper

  • Or there may be an inelastic collision, when the photon hits an atom and knocks out an electron—the old photoelectric effect.

    The Mercenaries

    Henry Beam Piper

  • "Well, you know what happens when a photon comes in contact with the atomic structure of matter," Kato said.

    The Mercenaries

    Henry Beam Piper

  • There were hundreds of scintillations, each caused by a nuclear particle or photon striking the screen.

    The Blue Ghost Mystery

    Harold Leland Goodwin


British Dictionary definitions for photon

photon

noun
  1. a quantum of electromagnetic radiation, regarded as a particle with zero rest mass and charge, unit spin, and energy equal to the product of the frequency of the radiation and the Planck constant
Show More
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 photon

n.

"unit of electromagnetic radiation," 1926 in modern sense, from photo- "light" + -on "unit."

Show More
Online Etymology Dictionary, © 2010 Douglas Harper

photon in Medicine

photon

(fōtŏn′)
n.
  1. The quantum of electromagnetic energy, generally regarded as a discrete particle having zero mass, no electric charge, and an indefinitely long lifetime.
Show More
Related formspho•tonic adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

photon in Science

photon

[fōtŏn′]
  1. The subatomic particle that carries the electromagnetic force and is the quantum of electromagnetic radiation. The photon has a rest mass of zero, but has measurable momentum, exhibits deflection by a gravitational field, and can exert a force. It has no electric charge, has an indefinitely long lifetime, and is its own antiparticle. See Note at electromagnetic radiation. See Table at subatomic particle.
Show More
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

photon in Culture

photon

[(foh-ton)]

The quantum, or bundle of energy, in which light and other forms of electromagnetic radiation are emitted. (See atom.)

Show More
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.