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

Airbus has initiated an urgent recall impacting up to 6,000 of its A320-family aircraft, following the discovery of a critical software issue linked to solar radiation interference, a move that threatens significant travel disruptions worldwide. —Jesus Mesa, MSNBC Newsweek, 28 Nov. 2025

Relapses are possible, as well as the development of other types of cancer due to her prolonged exposure to chemotherapy and radiation. —Luis Pascal, Miami Herald, 28 Nov. 2025

That information suggests that 3I/ATLAS's ices may have been shaped by harsher radiation environments around an older star, scientists said. —Sharmila Kuthunur, Space.com, 28 Nov. 2025

The end of whatever state came before the Big Bang (likely cosmic inflation) gave rise to a Universe full of particles, antiparticles, radiation, and all the ingredients necessary to make our existence possible. —Big Think, 27 Nov. 2025

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

• abdication
• aberration
• abjuration
• abnegation
• abrogation
• acceptation
• acclamation
• acclimation
• accusation
• activation
• actuation
• acylation

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