An antenna or aerial is a metal device made to send or receive radio waves. Many electronic devices like radio, television, radar, wireless LAN, cell phone, and GPS need antennas to do their job. Antennas work both in air and outer space.
The word 'antenna' is from Guglielmo Marconi's test with wireless equipment in 1895. For the test, He used a 2.5 meters long pole antenna with a tent pole called ' l'antenna centrale ' in Italian. So, his antenna was simply called ' l'antenna '. After that, the word 'antenna' became popular among people and had the meaning it has today. The plural of antenna is either antennas or antennae (U.S. and Canada tend to use antennas more than other places).
Each one is made to work for a specific frequency range. The antenna's length or size usually depends on the wavelength (1/frequency) it uses.

License information: CC BY-SA 3.0 and GFDL
MPAA: G
Go to source: https://simple.wikipedia.org/wiki/Antenna