ra·​di·​a·​tion | \ ˌrā-dē-ˈā-shən How to pronounce radiation (audio) \

Definition of radiation

1a : 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
2a : something that is radiated
b : energy radiated in the form of waves or particles
3 : radial arrangement

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Other Words from radiation

radiational \ ˌrā-​dē-​ˈā-​shnəl How to pronounce radiation (audio) , -​shə-​nᵊl \ adjective
radiationless \ ˌrā-​dē-​ˈā-​shən-​ləs How to pronounce radiation (audio) \ adjective
radiative \ ˈrā-​dē-​ˌā-​tiv How to pronounce radiation (audio) \ 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
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Recent Examples on the Web Bone scans are not routinely performed on or recommended for pregnant women, because of concerns about exposing the fetus to radiation. Paul Egan, Detroit Free Press, "Flint residents affected by water crisis may be getting exposed to harmful radiation," 28 Apr. 2021 The commission said someone being 30 meters away could still be exposed to radiation through the device. Mica Soellner, Washington Examiner, "Truck full of radioactive material hijacked in Mexico," 13 Apr. 2021 First contact came above Mars, where photons at energies comparable to the radiation from a nuclear bomb peppered a Russian particle detector on NASA’s Mars Odyssey probe. Joshua Sokol, Science | AAAS, "Nature’s most magnetic objects, ripped apart in starquakes, can unleash powerful flashes of light," 8 Apr. 2021 This results in delays in diagnosis, lapses in care, redundant appointments, excess imaging and unnecessary exposure to radiation, all leading to frustration among patients. Matthew Michela, Forbes, "Veterans Health Administration Opens Up: Tackling Interoperability In The Private Sector," 8 Apr. 2021 Here's how an Arizona bill to harshen crimes during protests could impact protesters The government exposed them to nuclear radiation. Yvonne Wingett Sanchez, The Arizona Republic, "Sen. Mark Kelly gives COVID-19 vaccinations to combat hesitancy: It's 'what’s going to get us through this'," 2 Apr. 2021 Just be sure to follow the safety instructions for your light to protect your eyes and minimize your exposure to radiation. Popsci Commerce Team, Popular Science, "Blacklight flashlights that reveal the secrets of your surroundings," 2 Mar. 2021 The report notes that some of the studies involved exposing military personnel in Eurasian communist countries to non-thermal microwave radiation. Beth Mole, Ars Technica, "US diplomats’ brain injuries may be from covert microwave attack, experts say," 10 Dec. 2020 The federal government has spent hundreds of millions of dollars paying Utahns and others in Western states who developed cancer after exposure to radiation from nuclear tests in earlier decades. The Salt Lake Tribune, "Congress moves to block renewed nuclear testing upwind from Utah," 4 Dec. 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'radiation.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of radiation

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

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Time Traveler for radiation

Time Traveler

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

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Statistics for radiation

Last Updated

1 May 2021

Cite this Entry

“Radiation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radiation. Accessed 7 May. 2021.

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More Definitions for radiation



English Language Learners Definition of radiation

: a type of dangerous and powerful energy that is produced by radioactive substances and nuclear reactions
medical : the use of controlled amounts of radiation for the treatment of diseases (such as cancer)
: energy that comes from a source in the form of waves or rays you cannot see


ra·​di·​a·​tion | \ ˌrā-dē-ˈā-shən How to pronounce radiation (audio) \

Kids Definition of radiation

1 : the process of giving off energy in the form of waves or particles
2 : something that is radiated (as light or X-rays)


ra·​di·​a·​tion | \ ˌrād-ē-ˈā-shən How to pronounce radiation (audio) \

Medical Definition of radiation

1 : energy radiated in the form of waves or particles
2a : the action or process of radiating with radiation of the pain there may be tenderness over the sciatic nerve— J. 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

Nglish: Translation of radiation for Spanish Speakers

Britannica English: Translation of radiation for Arabic Speakers

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