radiation
US /ˌreɪ.diˈeɪ.ʃən/
UK /ˌreɪ.diˈeɪ.ʃən/

1.
the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization
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Exposure to high levels of radiation can be harmful.
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The sun emits various forms of radiation, including ultraviolet light.
2.
the divergence of light or other electromagnetic radiation from a central point
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The radiation of heat from the fireplace warmed the room.
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The study focused on the radiation patterns of antennas.