radiation
noun
ra·di·a·tion
ˌrā-dē-ˈā-shən 
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
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
A little farther back, in 2023, a fascinating paper came out asserting that perhaps Hawking radiation isn’t just for black holes, but rather should apply to any massive object that led to spacetime curvature.
—
Ethan Siegel, Big Think, 19 Sep. 2025
Ultraviolet light interacts with matter more easily than X-rays, so the team theorizes that radiation from supermassive black hole accretion disks may more effectively push matter, leading to faster winds.
—Robert Lea, Space.com, 18 Sep. 2025
Harmon had mentally prepared herself for rounds of chemotherapy and radiation.
—Janine Rubenstein, PEOPLE, 18 Sep. 2025
Grant was diagnosed with B-cell acute lymphoblastic leukemia, a type of blood cancer that often requires chemotherapy and radiation.
—Kendall Malinchock, USA Today, 17 Sep. 2025
See All Example Sentences for radiation
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Ethan Siegel, Big Think, 19 Sep. 2025
Ultraviolet light interacts with matter more easily than X-rays, so the team theorizes that radiation from supermassive black hole accretion disks may more effectively push matter, leading to faster winds.
—Robert Lea, Space.com, 18 Sep. 2025
Harmon had mentally prepared herself for rounds of chemotherapy and radiation.
—Janine Rubenstein, PEOPLE, 18 Sep. 2025
Grant was diagnosed with B-cell acute lymphoblastic leukemia, a type of blood cancer that often requires chemotherapy and radiation.
—Kendall Malinchock, USA Today, 17 Sep. 2025
See All Example Sentences for radiation
Cite this Entry
“Radiation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/radiation. Accessed 20 Sep. 2025.
Copy CitationKids Definition
radiation
noun
ra·di·a·tion
ˌrād-ē-ˈā-shən
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
Medical Definition
radiation
noun
ra·di·a·tion
ˌrād-ē-ˈā-shən
1
: energy radiated in the form of waves or particles
2
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
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