Real Dictionary

radio
Radio is the broadcasting of programmes for the public to listen to, by sending out signals from a transmitter.

radio in American English
of, using, used in, sent by, or operated by radio
the practice or science of communicating over a distance by converting sounds or signals into electromagnetic waves and transmitting these directly through space, without connecting wires, to a receiving set, which changes them back into sounds, signals,
to send (a message, etc.) or communicate with (a person) by radio
adjective: pertaining to, used in, or sent by radio
intransitive verb: to transmit a message, music, etc., by radio
noun: wireless telegraphy or telephony
transitive verb: to transmit (a message, music, etc.) by radio

radio in British English
noun: the use of electromagnetic waves, lying in the radio-frequency range, for broadcasting, two-way communications, etc
verb: to transmit (a message) to (a person, radio station, etc) by means of radio waves

radio in Electrical Engineering
noun: Radio is the use of electromagnetic radiation to communicate electrical signals without wires, to create sound broadcasting, television, and radar.

radio in Hospitality
noun: A radio is the piece of equipment that you use in order to listen to radio programs.

radio- in American English
ray, raylike
combining form: 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

radio- in British English
combining form: denoting radio, broadcasting, or radio frequency