a combining form with the meanings “dealing with radiant energy” (radiometer), “employing or dealing with radio waves” (radioacoustics; radiolocation; radiotelephone), “emitting rays as a result of the breakup of atomic nuclei” (radioactive; radiocarbon), “characterized by, employing or dealing with such rays” (radiography; radiopaque; radiotherapy).
Origin of radio-
< French, combining form representing Latin radius beam, ray, radius
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for radio-
denoting radio, broadcasting, or radio frequencyradiogram
indicating radioactivity or radiationradiochemistry; radiolucent
indicating a radioactive isotope or substanceradioactinium; radiothorium; radioelement
Word Origin for radio-
from French, from Latin radius ray; see radius
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for radio-
word-forming element meaning 1. "ray, ray-like" (see radius); 2. "radial, radially" (see radial (adj.)); 3. "by means of radiant energy" (see radiate (v.)); 4. "radioactive" (see radioactive); 5. "by radio" (see radio (n.)).
Online Etymology Dictionary, © 2010 Douglas Harper
Medicine definitions for radio-
Radiation; radiant energy:radiometer.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.