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

preradio, adjective Unabridged


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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World English Dictionary
radio (ˈreɪdɪəʊ)
n , pl -os
1.  the use of electromagnetic waves, lying in the radio-frequency range, for broadcasting, two-way communications, etc
2.  an electronic device designed to receive, demodulate, and amplify radio signals from sound broadcasting stations, etc
3.  a similar device permitting both transmission and reception of radio signals for two-way communications
4.  the broadcasting, content, etc, of sound radio programmes: he thinks radio is poor these days
5.  a.  the occupation or profession concerned with any aspect of the broadcasting of sound radio programmes: he's in radio
 b.  (modifier) relating to, produced for, or transmitted by sound radio: radio drama
6.  radiotelegraph radiotelegraphy short for radiotelephone
7.  (modifier)
 a.  of, relating to, employed in, or sent by radio signals: a radio station
 b.  of, concerned with, using, or operated by radio frequencies: radio spectrum
8.  (modifier) (of a motor vehicle) equipped with a radio for communication: radio car
vb , -os, -os, -oing, -oed
9.  to transmit (a message) to (a person, radio station, etc) by means of radio waves
[C20: short for radiotelegraphy]

combining form
1.  denoting radio, broadcasting, or radio frequency: radiogram
2.  indicating radioactivity or radiation: radiochemistry; radiolucent
3.  indicating a radioactive isotope or substance: radioactinium; radiothorium; radioelement
[from French, from Latin radius ray; see radius]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

"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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American Heritage
Medical Dictionary

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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American Heritage
Science Dictionary
radio   (rā'dē-ō)  Pronunciation Key 
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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Example sentences
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.
They identify radio-equipped headgear allowing direct communication from coach to player.
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