A circuit is a complete loop or path that something travels along, returning to where it started.

In electronics, a circuit is the path electricity follows as it flows from a power source (like a battery), through wires and components (like light bulbs or motors), and back to the power source. If you've ever wired a simple flashlight, you've created a circuit: electricity flows from the battery through the switch, lights up the bulb, and returns to the battery. When there's a break anywhere in this loop, we call it an open circuit, and the electricity stops flowing. A closed circuit means the path is complete and electricity can flow.

The word also describes regular routes people travel. A judge might travel a circuit of courthouses in different towns, hearing cases in each location on a schedule. Professional tennis players compete on the international circuit, traveling from tournament to tournament around the world. Comic book conventions happen on a circuit too, with the same vendors and guests appearing in different cities throughout the year.

In both uses, the key idea is the same: a connected path that forms a loop or regular pattern. Whether it's electricity flowing through wires or a musician touring from city to city, a circuit means traveling a defined route and returning to the starting point.