The nomenclature of "exact differential equation" refers to the exact differential of a function. For a function F ( x 0 , x 1 , . . . , x n − 1 , x n ) {\displaystyle F(x_{0},x_{1},...,x_{n-1},x_{n})} , the exact or total derivative with respect to x 0 {\displaystyle x_{0}} is given by