The differentiation of a multivariate function with respect to one of its variable while the others are held constant. Consider the multivariate function f(x y z), the partial differentiation of f with respect to x is expressed as ∂f/∂x, during the partial differentiation with respect to x, y and z are treated as constants. The partial differentiation of f with respect to y and z are expressed as ∂f/∂y, and ∂f/∂z, respectively.The function f can be partially differentiated more than once. In general, the n^th partial differentiation of f with respect to x is expressed as ∂ⁿf/∂xⁿ.