Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English


English definition of “radiation”


noun [U]    /ˌreɪ·diˈeɪ·ʃən/
physics energy in the form of waves or particles (= any of the smallest pieces of matter that make up atoms ): Residents argued that electromagnetic radiation emitted by the radar towers might pose a health hazard .
(Definition of radiation noun from the Cambridge Academic Content Dictionary © Cambridge University Press)
Focus on the pronunciation of radiation

More American English definitions for “radiation”

Definitions of “radiation” in other dictionaries

Word of the Day

best man

a male friend or relation of the bridegroom who stands with him and helps him during a marriage ceremony

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More