Plain English Meaning
A small piece of quartz cut to vibrate at an exact frequency. Radios use it to stay locked on the right frequency without drifting.
Full Definition
A solid material whose atoms are arranged in a regular, repeating three-dimensional pattern. In aviation electronics, a small slice of quartz crystal is used to control the frequency of radio transmitters and receivers, because it vibrates at a very precise, stable rate when an electric voltage is applied to it.
Context Anchor
Seen in discussions of aircraft radios, navigation receivers, transmitters, clocks, and older frequency-control equipment.
Derivation
From the Greek 'krystallos,' meaning 'ice' or 'clear ice.' Early observers thought quartz was a kind of permanently frozen water. The aviation use comes from the discovery that quartz crystals vibrate at very steady rates when electrically excited -- making them ideal frequency references.
Why Pilots Care
Crystal-controlled radios stay on frequency reliably, which matters for clear ATC communication and accurate navigation signal reception. A drifting radio can mean missed calls or tuning the wrong station.
Analogy
A crystal works a little like a tuning fork for electronics. Once it is made for a certain rate, it helps the circuit keep that same steady beat.
Intuition Check
Crystal does not mean decorative glass here. In aviation electronics, it means a small frequency-control part, usually made from quartz or a similar material.
Example Sentence 1
The transmitter uses a quartz crystal to hold its frequency steady within a fraction of a hertz.
Example Sentence 2
Modern avionics use synthesized frequencies, but many legacy aircraft still rely on crystal-controlled transmitters for reliable operation.