1. A mutual relation between two circuits that permits energy transfer from one to another, through a wire, resistor, transformer, capacitor, or other device.

2. A hardware device used to make a temporary connection between two wires.

1. Any device that serves to connect the ends of adjacent parts, as railroad cars.

2. A metal collar with internal threads used to connect two sections of threaded pipe.

The mechanical fastening that connects shafts together for power transmission. Also known as shaft coupling.