radiation

Etymology

Borrowed from Latin radiatio, radiationis. By surface analysis, radiate + -ion.

noun

1. The shooting forth of anything from a point or surface, like diverging rays of light.
   heat radiation
2. The process of radiating waves or particles.
3. The transfer of energy via radiation.
4. Radioactive energy.
   It's Christmas at ground zero / And if the radiation level's OK / I'll go out with you / To see all the new / Mutations on New Year's Day 1986, "Weird Al" Yankovic (lyrics and music), “Christmas at Ground Zero”, in Polka Party!
5. (evolutionary theory, countable) A rapid diversification of an ancestral species into many new forms.
   So the question is: have plants and animals retained over this huge amount of time—whole radiations of mammals have come and gone in this period—have they retained these potentially costly characteristics? 2014, Elizabeth Kolbert, chapter 8, in The Sixth Extinction: An Unnatural History, Henry Holt and Company
   The second [canid group] is the radiation of dogs in South America that began when the first canids arrived about 3 Ma, after crossing the Panama land bridge (Fig. 5.4). 2016, Donald R. Prothero, The Princeton Field Guide to Prehistoric Mammals, page 136