Photon

How to spell photon

6 letters · 2 syllables

How to pronounce photon

Say the part in capitals loudest.

What does photon mean?

1. nounA single quantum, or indivisible packet, of light or other electromagnetic radiation.

Photon in a sentence

• Each photon carries a fixed amount of energy that depends on its frequency.

• The detector registers a faint signal when a single photon strikes the sensor.

Where does photon come from?

Language of origin: Greek

The word photon was coined relatively recently, in 1926, by the American physical chemist Gilbert N. Lewis, who built it from the Greek root phos (genitive photos), meaning 'light'. To this he added the suffix -on, the same ending used to name fundamental particles such as the electron and the proton, marking the photon as the basic quantum, or smallest packet, of light. That Greek root for light is the same one hiding in everyday words like photograph (literally 'light writing') and telephone's cousin photometer. Although the concept of light coming in discrete energy quanta dates to Einstein's work around 1905, the snappy name took two decades to arrive and then quickly stuck. The spelling stays close to its Greek source, so remembering the 'phot' in photograph is a reliable guide to the opening of photon.

How the word is built

• phot- (from Greek phos, photos: light)
• -on (particle suffix, as in electron, proton)