degrees of freedom, $$\nu$$

https://doi.org/10.1351/goldbook.D01572
A statistical quantity indicating the number of values which could be arbitrarily assigned within the specification of a system of observations. For simple @R05300@, with $$n$$ measurements and one estimated parameter (the mean), $$\nu =n- 1$$. 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 [Terms] [Paper]