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

Explanation

In physics, a photon is a tiny bundle of matter that transmits light. You can also think of photons as little bits of electromagnetic energy. Light is made up of small amounts of energy which are known as photons. You can tell how much radiation is being emitted by the number of photons — think of a dimmer on a light switch, with the brighter light emitting more photons. Albert Einstein was instrumental in developing the photon theory of light, although he used the term "the light quantum," rather than photon, which was first used in this sense around 1926.

Example Sentences

A photon, for example, comes from an open string vibrating in its simplest mode, while the graviton is thought to arise from a closed vibrating string.

From Science Daily • May 19, 2026

The device then distinguished different kinds of three photon W states.

From Science Daily • May 13, 2026

But the W state, another major type of multi photon entanglement, had remained out of reach.

From Science Daily • May 13, 2026

It could also support new quantum communication protocols, the transfer of multi photon entangled states, and new approaches to measurement based quantum computing.

From Science Daily • May 13, 2026

They suggested that in addition to the photon, there were three other spin-1 particles, known collectively as massive vector bosons, that carried the weak force.

From "A Brief History of Time: And Other Essays" by Stephen Hawking