property of a reference material, demonstrated by the closeness of agreement between the relation among the measurement results for a stated quantity in this material, obtained according to two given measurement procedures, and the relation obtained among the measurement results for other specified materials
NOTE 1 The reference material in question is usually a calibrator and the other specified materials are usually routine samples.
NOTE 2 The measurement procedures referred to in the definition are the one preceding and the one following the reference material (calibrator) in question in a calibration hierarchy (see ISO 17511).
NOTE 3 The stability of commutable reference materials should be monitored regularly.