ASME Y14.5 : Dimensioning and Tolerancing
The total amount a dimension or feature is permitted to vary. The tolerance is the difference between the maximum and minimum limits.
See Also:
Dimension, Feature, Directly Toleranced Dimension, Equal Bilateral Tolerance, Geometric Dimensions & Tolerances, Geometric Tolerance
Alternate Definitions:

DAU - A measure of the accuracy of the dimensions of a part.