radiation

plural radiations

1. countableuncountableThe shooting forth of anything from a point or surface, like diverging rays of light.

   The radiation of love from the crowd was addictive to the young singer-songwriters.

   1. abbreviationcountableellipsisoftenuncountableEllipsis of electromagnetic radiation.

      heat radiation

      Synonyms: EMR

2. countableuncountableThe process of radiating waves or particles.
3. countableuncountableThe transfer of energy via radiation.
4. countableuncountableRadioactive 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, “Christmas at Ground Zero”, in Polka Party!

5. countableevolutionary theoryA rapid diversification of an ancestral species into many new forms.

   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

   1 more example

   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