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English definition of “radiation”

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radiation

noun [U]  /ˌreɪ·diˈeɪ·ʃən/ us  
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.
(the sending out of) heat, light, or energy in waves: solar radiation
(Definition of radiation from the Cambridge Academic Content Dictionary © Cambridge University Press)
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