In simple terms, they are pieces of extremely fine wire formed into a series of tightly spaced U shapes.

This wire formed the vital portion of a dictograph connection.

On one side you see mostly lights; on the other, green wires form a climbing vine.

The two wires form a 'T' shape, hence the name.

These wires form a circuit like the one you might find in a flashlight.

Against a night sky, the live wires form an incandescent web - and a lovers' trap.

The wire forms the anode and the crystal forms the cathode.

The wire forms a small loop with a diameter of about 5 mm.

The struts and wire bracing of a typical biplane form a box girder.

It is called this because the two wires form a balanced loop through which both sides of the telephone call travel.