Radio refers to the technology of using radio waves to carry information, such as sound, by systematically modulating properties of electromagnetic energy waves transmitted through space.
The word "radio" is also used to mean:
1. A radio receiver - an electronic device that receives radio waves and converts them into sound
2. Radio broadcasting - the transmission of audio content to a wide audience
3. In chemistry, radio- is a prefix meaning "radiation" or "radioactive"
4. Slang for "cool" or "awesome" in some contexts