A statistical quantity indicating the number of values which could be arbitrarily assigned within the specification of a system of observations. For simple replication, with n measurements and one estimated parameter (the mean), ν = n- 1. More generally, for multivariable computations, the number of degrees of freedom equals the number of observations minus the number of fitted parameters.
Source:
PAC, 1994, 66, 595. 'Nomenclature for the presentation of results of chemical analysis (IUPAC Recommendations 1994)' on page 599 (https://doi.org/10.1351/pac199466030595)