radiation

noun

ra·​di·​a·​tion ˌrā-dē-ˈā-shən How to pronounce radiation (audio)
1
a
: the action or process of radiating
b
: the process of emitting radiant energy in the form of waves or particles
c(1)
: the combined processes of emission, transmission, and absorption of radiant energy
(2)
: the transfer of heat by radiation compare conduction, convection
2
a
: something that is radiated
b
: energy radiated in the form of waves or particles
3
: radial arrangement
4
radiational adjective
radiationless adjective
radiative adjective

Examples of radiation in a Sentence

She was exposed to high levels of radiation. He goes in for radiation next week. the sun's radiation of heat
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Crow subsequently underwent a lumpectomy in both breasts and seven weeks of radiation. Ashley Hume, FOXNews.com, 1 May 2025 The Minecraft-loving teen completed six weeks of radiation on April 4 and is now taking chemotherapy pills. Cara Lynn Shultz, People.com, 30 Apr. 2025 Errant Movements The Cosmos 2553 has been in orbit some 1,100 miles above Earth, in a hotspot of cosmic radiation that communications satellites typically avoid, Reuters said. Mohammed Soliman, MSNBC Newsweek, 28 Apr. 2025 This object has a bipolar, cylindrical outflow of gas, propelled by radiation and stellar winds from a hot white dwarf at the center. Alan Taylor, The Atlantic, 28 Apr. 2025 See All Example Sentences for radiation

Word History

First Known Use

15th century, in the meaning defined at sense 1a

Time Traveler
The first known use of radiation was in the 15th century

Browse Nearby Words

Cite this Entry

“Radiation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radiation. Accessed 4 May. 2025.

Kids Definition

radiation

noun
ra·​di·​a·​tion ˌrād-ē-ˈā-shən How to pronounce radiation (audio)
1
: the action or process of radiating
especially : the process of giving off radiant energy in the form of waves or particles
2
: something that is radiated
especially : energy radiated in the form of waves or particles
radiational
-shnəl How to pronounce radiation (audio)
-shən-ᵊl
adjective

Medical Definition

radiation

noun
ra·​di·​a·​tion ˌrād-ē-ˈā-shən How to pronounce radiation (audio)
1
: energy radiated in the form of waves or particles
2
a
: the action or process of radiating
with radiation of the pain there may be tenderness over the sciatic nerveJ. A. Key
b(1)
: the process of emitting radiant energy in the form of waves or particles
(2)
: the combined processes of emission, transmission, and absorption of radiant energy
3
: a tract of nerve fibers within the brain
especially : one concerned with the distribution of impulses arising from sensory stimuli to the relevant coordinating centers and nuclei
the optic radiations

More from Merriam-Webster on radiation

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