Radio broadcasting is defined as using radio waves to send transmissions to a large audience, who will listen to the transmission through a radio. The definition of radio broadcasting can be expanded by examining radio waves, radio transmitters and receivers. The radio broadcasting industry creates and licenses content to play on radio stations, which are received by radio receivers.
More like light than sound, radio waves are comparatively low frequency waves in the electromagnetic spectrum. Radio waves can be used to transmit information without wires. Data can be coded into the radio waves by modulating the waves. In addition to radio, devices like television and cellular phones use radio waves to send and receive information. You can use radio waves to broadcast to several devices or to communicate between just two devices.
A radio is a device that transmits or receives information via radio waves. Radios were originally used for sound information, but today's models also accommodate digital information. Early radio only supported sending "dot and dash" sounds. Radio that supports voice transmissions is called "radiotelephony."
What we consider a radio is a collection of different inventions created over several decades between the late 1800s and early 1900s. Heinrich Hertz is credited with theorizing the existence of radio waves in the mid 1860s, and Guglielmo Marconi is credited with creating the first radio transmitter and proving Hertz's theory.
Broadcast Archive curator Barry Mishkind defines broadcasting as transmissions intended to be received by a wide group of listeners. Mishkind's definition excludes transmissions that are from one destination to another and those that are overhead by an unintended audience as broadcasting. All radio transmissions could be considered broadcasts, because the signals are sent out in all directions, but that is not generally referred to as broadcasting.
The transmitter is the device that sends out the broadcast. Most people will never directly use a radio transmitter for broadcasting purposes (walkie-talkies and cell phones do not broadcast). However, hobbyist broadcasters can broadcast over a specific frequency using a device called a HAM radio.
The receiver is the device that receives and decodes the radio broadcast so that a person can listen to the transmitted information. Radio receivers are commonly referred to just by the word "radio." Most people are familiar with a radio receiver and might own several of them.