That part of a hardware or software system that is conceptually closest to the user; the user interface.
Used other than figuratively or idiomatically: see front, end.
A module or device that interacts with another to add a specific feature or function.
An electric vehicle that can be recharged from an external power source.
Anything that plugs into something.
Able to be extended with further components in a modular fashion.
Designed to be plugged into an electrical power outlet or circuit.