An antenna is a feeler found on the head of a bug. You know, the gross, creepy, pointy things they wave around and use as feelers or sensors. An antenna is also a device that sends radio and television signals.
The singular noun antenna is just one of the feelers on a bug’s head — a sensory wand the insect waves around to check out its surroundings. The plural of this antenna is antennae. (Those Greeks and their funny words!) The singular noun antenna is also the thing on top of your television or radio. The plural of this antenna is antennas.