Definition
An electric lamp that produces light by passing an electric current through a low-pressure mercury vapor inside a sealed glass tube. The current excites the mercury vapor, which emits ultraviolet radiation. This UV radiation strikes a phosphor coating on the inside of the tube, causing the phosphor to glow visibly.
Plain English
A glass tube that lights up when electricity passes through gas inside it, making a special coating on the inside of the tube glow.
Context Anchor
Seen in aircraft lighting, cabin lighting, instrument panel lighting, and maintenance discussions about lamps, wiring, or lighting failures.
Derivation
From the Latin 'fluor' (a flowing) via the mineral fluorite, which glows under ultraviolet light. 'Fluorescence' became the term for any material that glows when struck by certain types of energy. The lamp is named for the fluorescing phosphor coating that produces its light.
Why Pilots Care
Fluorescent lamps run cooler and use less power than incandescent bulbs of similar brightness, which matters in aircraft where electrical load and heat are limited. They also have a different color quality, which can affect how charts and instruments appear.
Intuition Check
Do not think of a fluorescent lamp as just any bright lamp. In this context, it means a specific type of electric light that uses excited vapor and a glowing coating, not a heated wire.
Example Sentence 1
The mechanic replaced a burned-out fluorescent lamp in the hangar before starting the night inspection.
Example Sentence 2
Maintenance replaced the flickering fluorescent lamp in the cabin before the next passenger flight.