Definition
An electric lamp that produces light by passing an electrical current through mercury vapor sealed inside a glass tube. The current excites the mercury atoms, causing them to emit a bright, bluish-white light. Mercury vapor lamps require a warm-up period to reach full brightness and need a brief cool-down before they will restrike after being switched off.
Plain English
A type of light bulb that makes light by sending electricity through mercury gas inside a sealed glass tube. It glows bluish-white, takes a minute or two to reach full brightness, and won't turn back on right away if you switch it off.
Context Anchor
Seen in discussions of airport, ramp, hangar, or older area-lighting equipment.
Derivation
Named for what's inside the lamp -- mercury, the silvery liquid metal, in vapor (gas) form. The lamp works because electricity flowing through that vapor makes it glow.
Why Pilots Care
These lamps deliver high-intensity, long-life illumination critical for safe night and low-visibility airport operations.
Intuition Check
Do not picture an ordinary household bulb with a glowing wire. A mercury vapor lamp makes light from energized gas, so its starting and warm-up behavior is different.
Example Sentence 1
The maintenance hangar was lit by mercury vapor lamps that took nearly five minutes to reach full brightness after being switched on.
Example Sentence 2
Maintenance replaced the burned-out mercury vapor lamp on the taxiway to restore full lighting coverage.