In statistics, the number of degrees of freedom is the number of values in the final calculation of a statistic that are free to vary.
The number of independent ways by which a dynamic system can move, without violating any constraint imposed on it, is called number of degrees of freedom. In other words, the number of degrees of freedom can be defined as the minimum number of independent coordinates that can specify the position of the system completely.
The degree of freedom represents the number of ways in which the expected classes are free to vary in the chi-square goodness-of-fit test.