Definition
A precision measuring instrument used to determine the size of an object — typically its outside diameter, inside diameter, or depth — to within a thousandth of an inch (0.001") or finer. It works by closing a calibrated screw spindle against the object and reading the measurement from graduations on the sleeve and thimble.
Plain English
A hand tool that measures small parts very precisely. You close it gently around the part and read the number off the scale.
Context Anchor
Seen in aircraft maintenance, especially when checking parts that must stay within exact size limits.
Derivation
From the Greek 'mikros' (small) and 'metron' (measure) — literally 'small measure.' The name reflects its purpose: measuring very small dimensions accurately.
Why Pilots Care
Accurate measurements ensure engine parts stay within safe tolerances and prevent failures.
Intuition Check
A micrometer is not a flight instrument and it does not measure altitude or pressure. In this context, it is a precise measuring tool used on aircraft parts.
Example Sentence 1
The mechanic used a micrometer to check the cylinder bore for wear before reassembling the engine.
Example Sentence 2
Before reassembly, each cylinder wall thickness was measured using a micrometer.