Fluorescent lamps are low pressure gas discharge lamps in which the invisible UV radiation generated by the discharge is converted into light with the aid of phosphors.

There are tubular, ring-shaped and U-shaped fluorescent lamps and also compact fluorescent lamps. The tube diameter is often expressed in mm (e.g. T5 = 16 mm, T8 = 25mm, T12 = 38mm).

Like all discharge lamps, fluorescent lamps cannot be operated directly on mains voltage and control gear is required between the mains supply and the lamp.