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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 Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for radio-


combining form
denoting radio, broadcasting, or radio frequency: radiogram
indicating radioactivity or radiation: radiochemistry, radiolucent
indicating a radioactive isotope or substance: radioactinium, radiothorium, radioelement
Word Origin
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
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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
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radio- in Medicine

radio- or radi-

  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.
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