Plain English Meaning
A small electronic part that gives off light when electricity flows through it. It does not have a glowing wire inside like an old-style bulb -- the light comes straight from the electronics.
Full Definition
A semiconductor device that emits visible or infrared light when an electric current passes through it in the forward direction. The light is produced directly by the movement of electrons across a junction inside the device, with no heated filament involved.
Context Anchor
Seen in aircraft electrical systems, cockpit indicator lights, annunciator panels, displays, and lighting equipment descriptions.
Derivation
From 'diode' (a two-terminal electronic part that allows current to flow one way only) plus 'light-emitting' (gives off light). Knowing it is a diode explains why polarity matters: connect it backwards and it will not light up.
Why Pilots Care
LEDs provide reliable, low-power, long-life lighting for critical cockpit instruments and exterior lights, reducing electrical load and maintenance.
Intuition Check
Do not think of a light-emitting diode as just a tiny light bulb. A light bulb glows from a hot filament; a light-emitting diode makes light electronically and normally works only when current flows through it in the correct direction.
Example Sentence 1
The master caution panel uses LEDs, so the warning lights stay bright and reliable for thousands of flight hours.
Example Sentence 2
During the night flight, the wingtip navigation lights used LEDs that remained bright without overheating.