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[rey-dee-oh] /ˈreɪ diˌoʊ/
noun, plural radios.
wireless telegraphy or telephony:
speeches broadcast by radio.
an apparatus for receiving or transmitting radio broadcasts.
a message transmitted by radio.
pertaining to, used in, or sent by radio.
pertaining to or employing radiations, as of electrical energy.
verb (used with object), radioed, radioing.
to transmit (a message, music, etc.) by radio.
to send a message to (a person) by radio.
verb (used without object), radioed, radioing.
to transmit a message, music, etc., by radio.
1910-15; shortening of radiotelegraph or radiotelegraphy
Related forms
preradio, adjective


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).
< French, combining form representing Latin radius beam, ray, radius Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Examples for radio
  • Salt water can catch a flame when exposed to certain radio waves, a chemist has confirmed.
  • Spiralling radio waves could revolutionize telecommunications.
  • Cellphones use ultra-high-frequency radio waves to connect with telecommunications networks.
  • radio communication at sea quickly evolved into an indispensable safety aid for mariners.
  • The radio waves that pulse from the poles are identical to each other.
  • Seismic waves, unlike radio waves, give a profile of water depth.
  • The difference is that radar depends on radio waves.
  • They identify radio-equipped headgear allowing direct communication from coach to player.
  • After all, the radio waves carrying the time signal must travel at the speed of light, regardless of the satellites' speed.
  • Visible light and radio waves do not or cannot escape from such regions.
British Dictionary definitions for radio


noun (pl) -os
the use of electromagnetic waves, lying in the radio-frequency range, for broadcasting, two-way communications, etc
Also called (esp Brit) wireless. an electronic device designed to receive, demodulate, and amplify radio signals from sound broadcasting stations, etc
a similar device permitting both transmission and reception of radio signals for two-way communications
the broadcasting, content, etc, of sound radio programmes he thinks radio is poor these days
  1. the occupation or profession concerned with any aspect of the broadcasting of sound radio programmes he's in radio
  2. (modifier) relating to, produced for, or transmitted by sound radio radio drama
  1. of, relating to, employed in, or sent by radio signals a radio station
  2. of, concerned with, using, or operated by radio frequencies radio spectrum
(modifier) (of a motor vehicle) equipped with a radio for communication radio car
verb -os, -oing, -oed
to transmit (a message) to (a person, radio station, etc) by means of radio waves
Word Origin
C20: short for radiotelegraphy


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
"wireless transmission with radio waves," 1907, abstracted from earlier combinations such as radiophone (1881) and radio-telegraphy (1898), from radio-, comb. form of radiation (q.v.). Use for "radio receiver" is first attested 1917; sense of "sound broadcasting as a medium" is from 1922. Wireless remained more widespread until World War II, when military preference for radio turned the tables. The verb is attested from 1919.
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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radio in Science
Noun  The equipment used to generate, alter, transmit, and receive radio waves so that they carry information.

Adjective  Relating to or involving the emission of radio waves.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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