photon

American  

[foh-ton] / ˈfoʊ tɒn /

noun

• photons
  plural

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

---

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

---

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

---

photon Cultural  

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

---

Other Word Forms

Noun Inflected Forms

• photons
  plural

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

See Examples For:

photon photons

Simplifying the steering system was an important part of achieving that size while retaining propulsion based on photon recoil.

From Science Daily ● Aug. 18, 2026

If we were to make a precise measurement of whether the photon is dwelling in the atoms, at each instant of time, we would prevent the atoms from interacting with the photon.

From Science Daily ● Aug. 4, 2026

Any single run of the experiment gives only a very rough indication of whether the photon dwelt in the atoms, but averaging millions of runs yields an accurate dwell time.

From Science Daily ● Aug. 4, 2026

In such cases, the photon is scattered, and fails to arrive at its Ithaca.

From Science Daily ● Aug. 4, 2026

They seemed to be complementary pieces making a whole, the way particle and wave manifestations together defined a photon.

From "Big Science" by Michael Hiltzik

However, the photons in each type of light fluctuate and interact in different ways.

From Science Daily ● Aug. 8, 2026

In this established optical process, a pump beam enters a nonlinear crystal, where individual photons can split into pairs that may become quantum entangled.

From Science Daily ● Aug. 8, 2026

Researchers have now demonstrated a striking alternative: sunlight itself can be used to generate quantum entanglement between photons.

From Science Daily ● Aug. 8, 2026

Sunlight, laser light, and fluorescent light are all made of photons.

From Science Daily ● Aug. 8, 2026

Again, the photons that are exchanged are virtual particles.

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