radiation

American  

[ray-dee-ay-shuhn] / ˌreɪ diˈeɪ ʃən /

noun

• radiations
  plural

1. Physics.

   1. the process in which energy is emitted as particles or waves.

   2. the complete process in which energy is emitted by one body, transmitted through an intervening medium or space, and absorbed by another body.

   3. the energy transferred by these processes.

2. the act or process of radiating.

3. something that is radiated.

4. radial arrangement of parts.

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radiation British  

/ ˌreɪdɪˈeɪʃən /

noun

1. physics

   1. the emission or transfer of radiant energy as particles, electromagnetic waves, sound, etc

   2. the particles, etc, emitted, esp the particles and gamma rays emitted in nuclear decay

2. Also called: radiation therapy. med treatment using a radioactive substance

3. anatomy a group of nerve fibres that diverge from their common source

4. See adaptive radiation

5. the act, state, or process of radiating or being radiated

6. surveying the fixing of points around a central plane table by using an alidade and measuring tape

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radiation Scientific  

/ rā′dē-ā′shən /

1. 1. Streams of photons, electrons, small nuclei, or other particles. Radiation is given off by a wide variety of processes, such as thermal activity, nuclear reactions (as in fission), and by radioactive decay.

   2. The emission or movement of such particles through space or a medium, such as air.

2. The use of such energy, especially x-rays, in medical diagnosis and treatment.

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radiation Cultural  

1. Energy sent out in the form of particles or waves. (See alpha radiation, beta radiation, blackbody, cosmic rays, electromagnetic radiation, fluorescence, gamma radiation, photon, and quanta.)

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Other Word Forms

Derived Forms

• interradiation
  noun
• nonradiation
  noun
• antiradiation
  adjective
• radiational
  adjective

Inflected Forms

Nouns

• radiations
  plural

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Etymology

Origin of radiation

First recorded in 1545–55; from Latin radiātiōn-, stem of radiātiō “beam, gleam, shine”; equivalent to radiate + -ion

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Explanation

Radiation is energy transmitted in waves or a stream of particles. The first thing you think of as radiation is probably X-rays, but what cooks your food in the microwave oven is also radiation. Radiation has some important medical uses, especially in the treatment of cancer, as "radiation therapy." It’s also associated with such horrors as "radiation sickness" — observed in people exposed to high levels of radiation, as in the aftermath of the 1986 explosion at the Chernobyl nuclear reactor, in the Ukraine. You can also use the word radiation, in more benign contexts, to describe something spreading out from a central point, as the radiation of warmth from your fireplace.

Example Sentences

See Examples For:

radiation radiations

Within 15 minutes, Ukraine's Air Force issued a statement saying the alert app had been compromised and clarifying there was no radiation threat.

From BBC ● Nov. 2, 2026

Ukraine’s air force quickly said there was no radiation threat and urged citizens to stay calm.

From The Wall Street Journal ● Nov. 2, 2026

Often described as the oldest light in the cosmos, this radiation provides a valuable record of conditions that existed shortly after the Big Bang.

From Science Daily ● Nov. 2, 2026

A cyberattack on Ukraine’s Air Alert app sent false warnings of radiation, chemical threats and street fighting to users in Kyiv.

From The Wall Street Journal ● Nov. 2, 2026

Dressed in full radiation suits, they headed for the emergency response center.

From "Meltdown" by Deirdre Langeland

There were radiations of hoofed mammals; of primates including our ancestors; of whales and dolphins; of the all-time biggest sharks.

From Salon ● Feb. 17, 2025

The link between a tendency to explore and colonize new environments and rapid evolution could help explain adaptive radiations in other species, says Daniel Moen, an evolutionary biologist at the University of California, Riverside.

From Science Magazine ● Apr. 24, 2024

The ultimate causes, or triggers, of adaptive radiations is one of the big mysteries in biology.

From Science Daily ● Feb. 22, 2024

The species depicted are only four from a very diverse lineage that contains many branches, dead ends, and adaptive radiations.

From Textbooks ● Apr. 25, 2013

So could radiations from certain rocks, or arsenic washed out of soil or rocks to contaminate food or water supplies.

From "Silent Spring" by Rachel Carson

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Related Words

• emission

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