When you have two pieces of equipment that can't be connected directly, you may need an adapter to plug one into another. You might need an adapter to connect your cellphone to a computer.
Computers, televisions, and cameras are just some of the devices that often require adapters to be charged or used in different ways. One common kind of adapter makes it possible to put a two-pronged plug into an outlet with three holes. A different way to use the word adapter is for a person who changes — or adapts — one work of art to fit in a different medium, like an adapter who writes an opera based on a comic book.