A coordinate system is a lot like an elevation map where the combination of a letter along one edge of the map, a number along the other, and elevations shown throughout uniquely describes each location on the map.

This letter/number/elevation combination is called a coordinate and represents a specific place relative to all others.
A coordinate measuring machine (CMM) works in much the same way as your finger when it traces map coordinates;
its three axes form the machine’s coordinate system. Instead of a finger, the CMM uses a probe to measure points on a workpiece.
Each point on the workpiece is unique to the machine’s coordinate system.
The CMM combines the measured points to form a feature that can now be related to all other features.
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