1. Energy that is radiated or transmitted in the form of rays or waves or particles
   "Harmful radiation from the sun can cause skin damage"
    
2. The act of spreading outward from a central source
   "The radiation of heat from the fire warmed the room"
    
3. The spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
   "radiation from the damaged nuclear plant posed environmental risks";
   - radioactivity
    
4. Syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); low doses cause diarrhoea 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";
   - radiation sickness, radiation syndrome
    
5. (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance
   "radiosensitive cancer cells can be treated with radiation"; "The oncologist recommended a course of radiation therapy for the tumour";
   - radiotherapy, radiation therapy, actinotherapy, irradiation
    
6. The spread of a group of organisms into new habitats
   "The radiation of finches in the Galapagos Islands is a classic example of adaptive evolution"
    
7. A radial arrangement of nerve fibers connecting different parts of the brain
   "The optic radiation carries visual information from the thalamus to the visual cortex"

Derived forms: radiations

Type of: action, activity, emanation, emission, energy, free energy, natural action, natural process, neural structure, spread, spreading, syndrome, therapy, treatment

Encyclopedia: Radiation, Radioactivity