Radiation

Part of speech: noun

Pronunciation: /ˌɹeɪ.diˈeɪ.ʃən/

Definitions

1. The process by which energy is emitted in waves or particles, often traveling through space or material mediums, and the phenomenon involving this energy transfer
2. Energy emitted in the form of electromagnetic waves or particles that can travel through various materials or vacuum, along with the effects caused by such emissions
3. The act of sending out energy by means of waves or particles ; the spread of energy in waves or particles through space or matter

Etymology: The Latin root of "radiation" is "radius," meaning a ray or spoke, which is why the word still carries the image of light and heat spreading outward from a single point. English took the term from Latin "radiatio," a noun built from the verb "radiare," to shine or emit rays. The Latin verb itself was formed from "radius," so the word is essentially a description of something shooting out in every direction. The modern sense is far narrower than the Latin image suggests. Where "radiare" simply meant to beam or gleam, English "radiation" now covers energy moving as waves or particles, from the warmth of sunlight to the emissions of a radioactive material. The shift reflects how the physical sciences came to describe light and heat as streams of energy rather than as rays of vision. The word's pieces are easy to read: "radiate" plus the suffix "-ion," which turns a verb into a noun of action or process. So "radiation" literally names the act of radiating, and the abstract physics meaning grew out of that plain verb.

Synonyms: radiant energy, emission, radiance