Definition of radiation in English:



mass noun
  • 1Physics
    The emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles which cause ionization.

    • ‘We now know that invisible forces do control some things: gravity, radiation, electricity.’
    • ‘The board does say that there is still a need for further research into other concerns over the safety of microwave radiation.’
    • ‘When taken up by obstacles, beta particles produce a more penetrative secondary radiation known as bremsstrahlung.’
    • ‘Huygens stated that an expanding sphere of light behaves as if each point on the wave front were a new source of radiation of the same frequency and phase.’
    • ‘Because it uses sound waves instead of radiation, ultrasound is safer than X-rays.’
    discharge, release, outpouring, outflow, outrush, leak, excretion, secretion, ejection
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    1. 1.1 The energy transmitted by radiation.
      ‘background radiation’
      as modifier ‘the radiation dose’
      count noun ‘ultraviolet and infrared radiations’
      • ‘A radioactive source will emit these radiations at various frequencies, depending on its activity and its decay mode.’
      • ‘This foil doesn't do very well in the air, but it protected it from meteorites and from the ultraviolet radiations from the sun.’
      • ‘The total spectrum of solar radiation comprises ultraviolet radiations, visible light, and infra-red radiations, in order of increasing electromagnetic wavelengths.’
      • ‘It is these materials that emit gamma rays, high energy radiation that can pass right through your skin.’
      • ‘Radioactivity is the process of emission of radiation as a radioactive material changes form, often to a different element.’
      transference, transferral, passing on, communication, conveyance, imparting, channelling, carrying, relaying, dispatch, mediation
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  • 2Biology
    Divergence out from a central point, in particular evolution from an ancestral animal or plant group into a variety of new forms.

    ‘evolution is a process of radiation not progression’
    • ‘Rate variation among lineages is the footprint of selection and can be indicative of species radiations or differential structural constraints.’
    • ‘This famous site in British Columbia has yielded much fundamental information on the early radiation of the major animal groups.’
    • ‘Each of these pulses is a major evolutionary radiation of the Theropsid lineage.’
    • ‘The radiation of modern felines began with the divergence of the Panthera lineage.’
    • ‘During the Oligocene, the South American rodents began their great evolutionary radiation.’


Late Middle English (denoting the action of sending out rays of light): from Latin radiatio(n-), from radiare ‘emit rays’ (see radiate).