Etymology
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radio (n.)

"wireless transmission of voice signals with radio waves," 1907, abstracted or shortened from earlier combinations such as radio-receiver (1903), radiophone "instrument for the production of sound by radiant energy" (1881), radio-telegraphy "means of sending telegraph messages by radio rather than by wire" (1898), from radio- as a combining form of Latin radius "beam" (see radius). Use for "radio receiver" is attested by 1913; sense of "sound broadcasting as a medium" also is from 1913.

That winter, however—the winter of 1921-22—[radio] came with a rush. Soon everybody was talking, not about wireless telephony, but about radio. A San Francisco paper described the discovery that millions were making: "There is radio music in the air, every night, everywhere. Anybody can hear it at home on a receiving set, which any boy can put up in an hour." In February President Harding had an outfit installed in his study, and the Dixmoor Golf Club announced that it would install a "telephone" to enable golfers to hear church services. [Frederick Lewis Allen, "Only Yesterday: An Informal History of the 1920's," 1931]
It is not a dream, but a probability that the radio will demolish blocs, cut the strings of red tape, actuate the voice "back home," dismantle politics and entrench the nation's executive in a position of power unlike that within the grasp of any executive in the world's history. [The Reading Eagle, Reading, Pa., U.S.A., March 16, 1924]

As late as July 1921 the New York Times was calling it wireless telephony, and wireless remained widespread until World War II, when military preference for radio established it as the word. As an adjective by 1912, "by radio transmission;" meaning "controlled by radio" is from 1974. Radio _______ as the proper name of a particular radio station or service, "radio station or service from _______" is by 1920. A radio shack (1946) was a small outbuilding housing radio equipment.

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radio (v.)

"transmit by radio," 1916, from radio (n.). Related: Radioed; radioing. An earlier verb in the same sense was marconi (1908), from the name of Italian inventor Guglielmo Marconi (1874-1937), pioneer of wireless telegraphy.

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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.)).
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radio-telephone (n.)

"telephone link through which the signal is transmitted partly by radio," 1900, from radio (n.) + telephone (n.).

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clock-radio (n.)

"combined bedside radio and alarm clock which can be set to turn on the radio instead of sounding the alarm," 1946, from clock (n.1) + radio (n.).

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radiotherapy (n.)

"treatment of disease by means of x-rays," 1902, from radio- + therapy.

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radioisotope (n.)

"a radioactive isotope," 1946, from radio-, combining form of radiation, + isotope.

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radioscopy (n.)

"examination by means of x-rays," 1896, from radio- + -scopy.

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radiocast (n.)

"a radio broadcast," 1924, from radio (n.) + ending from broadcast. As a verb by 1931.

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wireless (adj.)
1894, in reference to as a type of telegraph, from wire (n.) + -less. As a noun, "radio broadcasting," attested from 1903, subsequently superseded by radio.
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