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

The chip also incorporates high-speed sensors capable of measuring photon lifetime with extremely high temporal precision.

From Science Daily • May 26, 2026

According to the researchers, sunlight's broad spectrum helps support quasi-phase matching inside the nonlinear crystal, allowing the production of large numbers of position-correlated photon pairs.

From Science Daily • May 18, 2026

The photon energy of 8.2 kiloelectronvolts matches a specific electronic transition in these ions, a process known as resonant absorption.

From Science Daily • May 1, 2026

Instead of relying on a single state determined by one photon, these systems create interconnected states across multiple particles.

From Science Daily • Apr. 30, 2026

As an electron sits in the vacuum, it occasionally absorbs or spits out one of these particles, such as a photon.

From "Zero: The Biography of a Dangerous Idea" by Charles Seife