radiation

/ˈreɪdiˌeɪʃən/

/reɪdiˈeɪʃɪn/

Other forms: radiations

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.

Definitions of radiation

1. noun

   the act of spreading outward from a central source
   types:

   bombardment

   the act (or an instance) of subjecting a body or substance to the impact of high-energy particles (as electrons or alpha rays)

   type of:

   emanation, emission

   the act of emitting; causing to flow forth
2. noun

   a radial arrangement of nerve fibers connecting different parts of the brain
   type of:

   neural structure

   a structure that is part of the nervous system
3. noun

   the spread of a group of organisms into new habitats
   types:

   adaptive radiation

   the development of many different forms from an originally homogeneous group of organisms as they fill different ecological niches

   type of:

   spread, spreading

   process or result of distributing or extending over a wide expanse of space

   action, activity, natural action, natural process

   a process existing in or produced by nature (rather than by the intent of human beings)
4. noun

   energy that is radiated or transmitted in the form of rays or waves or particles
   types:

   ionizing radiation

   high-energy radiation capable of producing ionization in substances through which it passes

   cosmic radiation

   radiation coming from outside the solar system

   electromagnetic radiation, electromagnetic wave, nonparticulate radiation

   radiation consisting of waves of energy associated with electric and magnetic fields resulting from the acceleration of an electric charge

   solar radiation

   radiation from the sun

   actinic radiation, actinic ray

   electromagnetic radiation that can produce photochemical reactions

   alpha radiation, alpha ray

   the radiation of alpha particles during radioactive decay

   beam, electron beam, ray

   a group of nearly parallel lines of electromagnetic radiation

   beta radiation, beta ray, electron radiation

   radiation of beta particles during radioactive decay

   black-body radiation, blackbody radiation

   the electromagnetic radiation that would be radiated from an ideal black body; the distribution of energy in the radiated spectrum of a black body depends only on temperature and is determined by Planck's radiation law

   CBR, CMB, CMBR, cosmic background radiation, cosmic microwave background, cosmic microwave background radiation

   (cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2.725 kelvin

   cosmic ray

   highly penetrating ionizing radiation of extraterrestrial origin; consisting chiefly of protons and alpha particles; collision with atmospheric particles results in rays and particles of many kinds

   Hertzian wave

   an electromagnetic wave generated by oscillations in an electric circuit

   gamma radiation, gamma ray

   electromagnetic radiation emitted during radioactive decay and having an extremely short wavelength

   line

   a single frequency (or very narrow band) of radiation in a spectrum

   microwave

   a short electromagnetic wave (longer than infrared but shorter than radio waves); used for radar and microwave ovens and for transmitting telephone, facsimile, video and data

   neutron radiation

   radiation of neutrons (as by a neutron bomb)

   radio emission, radio radiation, radio wave

   an electromagnetic wave with a wavelength between 0.5 cm to 30,000 m

   insolation

   incident solar radiation

   flare, solar flare

   a sudden eruption of intense high-energy radiation from the sun's surface; associated with sunspots and radio interference

   solar prominence

   large eruptions of luminous hydrogen gas that rise thousands of kilometers above the chromosphere

   solar wind

   a stream of protons moving radially from the sun

   X ray, X-radiation, X-ray, roentgen ray, x-ray

   electromagnetic radiation of short wavelength produced when high-speed electrons strike a solid target

   type of:

   energy, free energy

   (physics) a thermodynamic quantity equivalent to the capacity of a physical system to do work; the units of energy are joules or ergs
5. noun

   the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
   synonyms: radioactivity

   types:

   corpuscular radiation, particulate radiation

   a stream of atomic or subatomic particles that may be charged positively (e.g. alpha particles) or negatively (e.g. beta particles) or not at all (e.g. neutrons)

   alpha radiation, alpha ray

   the radiation of alpha particles during radioactive decay

   beta radiation, beta ray, electron radiation

   radiation of beta particles during radioactive decay

   neutron radiation

   radiation of neutrons (as by a neutron bomb)

   type of:

   emission

   the release of electrons from parent atoms
6. noun

   (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
   synonyms: actinotherapy, irradiation, radiation therapy, radiotherapy

   types:

   phototherapy

   the use of strong light to treat acne or hyperbilirubinemia of the newborn

   Curietherapy, radium therapy

   the use of radium in radiation therapy

   X-ray therapy

   the therapeutic use of X rays

   type of:

   therapy

   (medicine) the act of caring for someone (as by medication or remedial training etc.)
7. noun

   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”

   synonyms: radiation sickness, radiation syndrome

   type of:

   syndrome

   a pattern of symptoms indicative of some disease