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1. The act or process of radiating: the radiation of heat and light from a fire.
a. Emission or propagation of energy in the form of waves or particles.
b. Energy radiated or transmitted in the form of waves or particles.
c. A stream of particles or electromagnetic waves emitted by the atoms and molecules of a radioactive substance as a result of nuclear decay.
a. The act of exposing or the condition of being exposed to such energy.
b. The application of such energy, as in medical treatment.
4. Anatomy Radial arrangement of parts, as of a group of nerve fibers connecting different areas of the brain.
5. Adaptive radiation
ra′di·a′tion·al, ra′di·a′tive adj.
(General Physics) physics emitting or causing the emission of radiation: a radiative collision.