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photon

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Etymology and origin of the English word photon

Confidence
Established
Formation
Derivation
First attested
1916 L. T. Troland
Ultimate origin
Ancient Greek φῶς

Pronunciation

  • /ˈfəʊtɒn/[1]

Etymology

It is formed from English photo- + -on,[2][3][4][5][6] the first part from Ancient Greek φῶς (phôs, “light”).[7][8][4] The ending follows electron,[7][8] or, in Barnhart's view, proton.[6]

Earliest recorded meaning

A unit of light reaching the retina, now called the troland: L. T. Troland, 1916.[2][5]

Semantic evolution

The physicist's sense, a quantum of light or other electromagnetic radiation, is from 1926, in G. N. Lewis's letter to Nature;[2][6][4] it soon displaced the earlier units, and the OED marks the sense "unit of retinal illumination" as now rare.[2][3] In 1921 J. Joly had used photon for the least stimulus that produces a signal in a fibre of the optic nerve.[2] Dictionary.com dates the word to 1900–05.[9] Photonic and photonics, the technology of light, are from the mid 20th century.[3][4]

Timeline

  • 1916 – a unit of retinal illumination.[2][5]
  • 1921 – Joly's term for the least stimulus to the optic nerve.[2]
  • 1926 – a quantum of electromagnetic radiation.[2][6][4]

Meanings

Noun

  1. A quantum of electromagnetic radiation such as light, treated as a particle with no mass or charge, whose energy is proportional to the frequency of the radiation.[10][5][2]
  2. (now rare) A unit of retinal illumination; a troland.[2][5][3]

Word family

  • photonic
  • photonics

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  4. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  5. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  6. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  7. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
  8. ^ a b The Chambers Dictionary (2014), 13th ed., Edinburgh: Chambers
  9. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  10. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
Cite this entry

“Photon.” Etymologically, 31 Oct. 2026, etymologically.com/en/photon. Accessed 1 Nov. 2026.

Last edited on . ·