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

4

: adaptive radiation

radiational

ˌrā-dē-ˈā-sh(ə-)nəl 

adjective

radiationless

ˌrā-dē-ˈā-shən-ləs 

adjective

radiative

ˈrā-dē-ˌā-tiv 

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

The quest for 500 million flies The only way the US has succeeded in eradicating screwworm is by breeding millions of flies, sterilizing them using radiation and dropping them in areas with infestations. — Jen Christensen, CNN Money, 7 Sep. 2026

Advancing heart care Transcatheter structural heart surgeries use X-ray fluoroscopy, exposing both the patient and surgical staff to radiation. — Mrigakshi Dixit, Interesting Engineering, 7 Sep. 2026

Working with a ship that uses an advanced civilian nuclear reactor, the project is looking at what port facilities will be needed and the radiation safety measures tailored for a high-density container terminal. — New Atlas, 4 Sep. 2026

Such color variations are thought to be associated with camouflage, protection against parasites and ultraviolet radiation, and the effects of pleiotropic genes (genes that influence more than one, usually unrelated, physical trait or phenotype). — Encyclopedia Britannica, 3 Sep. 2026

Word History

First Known Use

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

Phrases Containing radiation

• adaptive radiation
• anti-radiation
• background radiation
• Cerenkov radiation
• cosmic background radiation
• electromagnetic radiation
• gamma radiation
• gravitational radiation
• radiation sickness
• radiation therapy
• secondary radiation
• synchrotron radiation
• x-radiation

Rhymes for radiation

• ablation
• aeration
• bination
• carnation
• cassation
• castration
• causation
• centration
• cessation
• cetacean
• chelation
• citation

Kids 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

radiational

-shnəl 

-shən-ᵊl

adjective

Medical Definition

radiation

noun

ra·​di·​a·​tion ˌrād-ē-ˈā-shən 

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 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