AskDefine | Define radiation

Dictionary Definition



1 energy that is radiated or transmitted in the form of rays or waves or particles
2 the act of spreading outward from a central source
3 syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); low doses cause diarrhea and nausea and vomiting and sometimes loss of hair; greater exposure can cause sterility and cataracts and some forms of cancer and other diseases; severe exposure can cause death within hours; "he was suffering from radiation" [syn: radiation sickness, radiation syndrome]
4 the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay [syn: radioactivity]
5 the spread of a group of organisms into new habitats
6 a radial arrangement of nerve fibers connecting different parts of the brain
7 (medicine) the treatment of disease (especially cancer) by exposure to radiation from a radioactive substance [syn: radiotherapy, radiation therapy, actinotherapy, irradiation]

User Contributed Dictionary



Latin radiatio: compare with French radiation.


  • /ˌreɪdiˈeɪʃən/
  • /%reIdi"eIS@n/
IPA: WEAE /ɹaɪ.diˈaɪ.ʃən/


  1. The shooting forth of anything from a point or surface, like the diverging rays of light; as, the radiation of heat.
  2. The process of radiating waves or particles.
  3. The transfer of energy via radiation (as opposed to convection or conduction)
  4. Radioactive energy


Extensive Definition

Radiation, as used in physics, is energy in the form of waves or moving subatomic particles emitted by an atom or other body as it changes from a higher energy state to a lower energy state. Radiation can be classified as ionizing or non-ionizing radiation, depending on its effect on atomic matter. The most common use of the word "radiation" refers to ionizing radiation. Ionizing radiation has enough energy to ionize atoms or molecules while non-ionizing radiation does not. Radioactive material is a physical material that emits ionizing radiation.

Types of Radiation

There are three principal types of ionizing radiation: alpha, beta and gamma radiation. They are all emitted from the nucleus of an unstable atom. Less commonly encountered are spontaneous nuclear fission; positron emission, which is utilized in positron emission tomography; and neutron emission. Electron capture results in the spontaneous emission of an X-ray. Certain isotopes of radium have a decay mode where they emit an entire 12C6 nucleus.


Wilhelm Roentgen is credited with the discovery of X-Rays. Henri Becquerel found that uranium salts caused fogging of an unexposed photographic plate, and Marie Curie discovered that only certain elements gave off these rays of energy. She named this behaviour radioactivity.
In December of 1898, Marie Curie and Pierre Curie discovered radium in pitchblende. This new element was two million times more radioactive than uranium, as described by Marie.

See also

radiation in Arabic: إشعاع
radiation in Catalan: Radiació
radiation in Czech: Záření
radiation in Danish: Stråling
radiation in German: Strahlung
radiation in Spanish: Radiación
radiation in Esperanto: Radiado
radiation in French: Rayonnement
radiation in Galician: Radiación
radiation in Icelandic: Geislun
radiation in Italian: Radiazione
radiation in Hebrew: קרינה
radiation in Malay (macrolanguage): Sinaran
radiation in Dutch: Straling
radiation in Japanese: 放射
radiation in Norwegian: Stråling
radiation in Norwegian Nynorsk: Stråling
radiation in Polish: Promieniowanie
radiation in Portuguese: Radiação
radiation in Russian: Излучение
radiation in Simple English: Radiation
radiation in Slovenian: Sevanje
radiation in Serbian: Зрачење
radiation in Finnish: Säteily
radiation in Swedish: Strålning
radiation in Turkish: Işınım
radiation in Urdu: اشعاع

Synonyms, Antonyms and Related Words

X ray, actinic ray, actinism, arc lighting, asteroids, atomic beam, atomic ray, attenuation, aurora particles, beam, beam of light, black and white, blackout, broadcast, broadcasting, chiaroscuro, circumfusion, contrast, cosmic particles, cosmic ray bombardment, decorative lighting, diffraction, diffusion, dilution, direct lighting, dispensation, dispersal, dispersion, dissemination, dissipation, distribution, divergence, electric lighting, emanation, emission, enlightenment, evaporation, expansion, festoon lighting, floodlighting, fluorescent lighting, fragmentation, gamma ray, gaslighting, gleam, glow lighting, highlight, highlights, illumination, incandescent lighting, indirect lighting, infrared ray, intergalactic matter, invisible radiation, irradiance, irradiancy, irradiation, leam, light, light and shade, light source, lighting, luminous energy, meteor dust impacts, meteors, overhead lighting, patch, pencil, peppering, photon, photosensitivity, propagation, publication, radiance, radiancy, radiant energy, radiorays, radius, ray, ray of light, ribbon, ribbon of light, scattering, scatterment, shedding, shotgun pattern, sidelight, solar rays, sowing, space bullets, spattering, splay, spoke, spot lighting, spread, spreading, sprinkling, stage lighting, streak, stream, stream of light, streamer, strewing, strip lighting, the bends, tonality, ultraviolet ray, violet ray, visible radiation, volatilization, weightlessness
Privacy Policy, About Us, Terms and Conditions, Contact Us
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2
Material from Wikipedia, Wiktionary, Dict
Valid HTML 4.01 Strict, Valid CSS Level 2.1