photon

American  

[foh-ton] / ˈfoʊ tɒn /

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. γ

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photon British  

/ ˈfəʊtɒn /

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

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photon Scientific  

/ fō′tŏn′ /

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.

2. See Note at electromagnetic radiation See Table at subatomic particle

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photon Cultural  

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

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Etymology

Origin of photon

First recorded in 1900–05; phot- + -on ¹

Example Sentences

When electrons absorb a photon and are emitted from a material, they carry information encoded in their spin.

From Science Daily • Feb. 9, 2026

An orderly photon stream is easier to manage and scale, and it also improves security.

From Science Daily • Dec. 23, 2025

This hybrid approach is the key to success: it combines the extreme sensitivity of photon detection with the ability to "recover" the calibration capabilities of the Autler-Townes method even for the weakest signals.

From Science Daily • Dec. 13, 2025

The newly formed CZT, a semiconductor, can detect tiny photon particles in X-rays and gamma rays with incredible precision – like a highly specialised version of the light-sensing, silicon-based image sensor in your smartphone camera.

From BBC • Dec. 11, 2025

Their goal was to investigate the structure of light by measuring the interval from the moment a quantum particle of light, a photon, strikes a target to the emission of an electron from its surface.

From "Big Science" by Michael Hiltzik