Fluorescent-lamp definition

A glass tube coated on the inside with a fluorescent substance that gives off a bright light (fluorescent light) when a vapor, usually mercury vapor, in the tube is acted upon by a stream of electrons from the cathode.

An electric lamp that produces light through fluorescence. In most fluorescent lamps, a mixture of argon and mercury gas contained in a glass bulb is stimulated by an electric current, producing ultraviolet rays. These rays strike a fluorescent phosphor coating on the interior surface of the bulb, causing it to emit visible light. Fluorescent lamps are much more efficient than incandescent lamps because very little energy is lost as heat.