What is the difference between concentricity and position for controlling coaxiality?

Concentricity controls the median points of a feature of size relative to a datum axis, requiring time-consuming CMM measurements of multiple cross-sections. Position controls the axis of a feature relative to datums, which is easier to inspect using functional gauges or simpler CMM routines. Position with MMC modifier is preferred for most applications as it provides functional control and allows bonus tolerance. Concentricity is reserved for situations requiring true center-to-center balance, like high-speed rotating components.