ETYM Latin radiatio: cf. French radiation.
In physics, emission of radiant energy as particles or waves—for example, heat, light, alpha particles, and beta particles (see electromagnetic waves and radioactivity). See also atomic radiation.
Of the radiation given off by the Sun, only a tiny fraction of it, called insolation, reaches the Earth’s surface; much of it is absorbed and scattered as it passes through the atmosphere. The radiation given off by the Earth itself is called (ground radiation).
1. The act of radiating.
2. The physical phenomenon of radiating energy in the form of waves or particles.