radiation

American  

[rey-dee-ey-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.

---

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

---

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.

---

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.)

---

Other Word Forms

Derived Forms

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

Inflected Forms

Nouns

• radiations
  plural

Etymology

Origin of radiation

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

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

Instead, they emit a faint form of radiation that slowly drains their energy, causing them to shrink and eventually disappear.

From Science Daily • Jul. 5, 2026

But Kryptonite radiation got to Kara’s parents anyway; they sent her to Earth as a teenager, it had a terrible impact — blah, blah, you get the picture.

From Salon • Jun. 27, 2026

This absorbs radiation more quickly, meaning extreme melting produces an accelerating feedback effect, worsening the situation even further.

From Barron's • Jun. 27, 2026

Even then, only part of that UV radiation is practical for technological applications.

From Science Daily • Jun. 26, 2026

With radiation levels at 44.7 mSv per hour, people would reach the emergency exposure maximum in less than six hours.

From "Meltdown" by Deirdre Langeland

Related Words

• emission