# photon

/ˈfoʊˌtɑn/ (US) · /fˈəʊtɒn/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/photon
Updated: 2026-08-15

## Definition

a tiny particle of light. It is the smallest possible piece of light energy.

For teachers: the quantum of the electromagnetic field, including electromagnetic radiation such as light. It carries energy proportional to the radiation frequency and has zero rest mass.

## Examples

- A photon is a tiny particle of light.
- When a photon hits a solar panel, it can knock an electron loose to create an electric current.
- In quantum mechanics, light exhibits both wave-like and particle-like properties, with the photon representing the discrete packet of energy that mediates electromagnetic interactions.

## Usage notes

- Commonly used in physics and optics; often appears in the plural when discussing light intensity.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.