Definition
On aircraft instruments, markings are the colored arcs, lines, and bands placed on the face of a gauge or dial to indicate operating ranges, limits, and caution areas defined in the Airplane Flight Manual. Common examples include the green arc (normal operating range), yellow arc (caution range), red line (never-exceed or maximum/minimum limit), and white arc (flap operating range on an airspeed indicator).
Plain English
The colored stripes and lines painted on the face of cockpit gauges that tell you, at a glance, which readings are safe, which require caution, and which must never be exceeded.
Context Anchor
In the Airplane Flight Manual (AFM), markings are listed as part of the required information that must appear on the aircraft, especially near controls, gauges, and other places the pilot checks during operation.
Derivation
Markings comes from mark, an old word for a sign, boundary, or visible trace. That helps in aviation because these marks make important limits and warnings visible to the pilot.
Why Pilots Care
Markings allow immediate recognition of airspeed, powerplant, and structural limits, reducing the chance of inadvertent exceedance that could damage the aircraft or compromise safety.
Intuition Check
Do not think of markings as decoration or paint design. In aviation, markings are required information that identifies things, shows limits, or warns the pilot.
Example Sentence 1
Before takeoff, the pilot scanned the engine instruments and confirmed all needles were within the green markings.
Example Sentence 2
All required cockpit markings listed in the AFM must remain legible for the aircraft to remain airworthy.