A number of turns of wire used to introduce inductance into an electric circuit, to produce magnetic flux, or to react mechanically to a changing magnetic flux.

In high-frequency circuits, a coil may be only a fraction of a turn.

1. Something that inducts, especially a device that functions by, or introduces, inductance into a circuit.
2. The property of an electric circuit, or device, whereby an electromotive force is created by a change of current in it or in a circuit near it.