The uncertainty of measurement: „parameter, associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand” (VIM 3.9)
The spreading of the calibration (do not belong to legal metrology) increased the public interest significantly for the uncertainty of measurement, since the measurement uncertainty is one of the most important qualitative features of the calibration.
Internationally widely accepted document, the Guide to the Expression of Uncertainty in Measurement (GUM), describes the method of the determination of the measurement uncertainty. The EA-4/02 Recommendation explains the base of GUM in detail.
Related side:
International Vocabulary of Basic and General Terms in Metrology
(Nemzetközi metrológiai értelmező szótár, OMH-MTA-MMSZ 1998)