A deviation from the correct value. Errors arise (a) because the problem description is not exact, as when the data are not exact (inherent error); (b) because the method used is not exact, as when an exact solution would require an unacceptably large number of calculations (method error); and (c) because of round-off errors (computational error). Gross errors are the results of blunders or mistakes. See round-off error, truncation error, random error, systematic, accuracy, and probable error. Error differs from uncertainty, which is the precision with which a measurement or value is known.