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definitions

radio-

  1. 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. 2018
British Dictionary definitions for radio-

radio-

combining form
  1. denoting radio, broadcasting, or radio frequencyradiogram
  2. indicating radioactivity or radiationradiochemistry; radiolucent
  3. 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
radio- in Medicine

radio-

pref.
  1. Radiation; radiant energy:radiometer.
  2. Radioactive:radiochemistry.
  3. Radius:radiobicipital.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.