Partial Derivative -- from Wolfram MathWorld

Partial derivatives are defined as derivatives of a function of multiple variables when all but the variable of interest are held fixed during the differentiation. (1) The above partial derivative is sometimes denoted f_(x_m) for brevity. Partial derivatives can also be taken with respect to multiple variables, as denoted for examples (partial^2f)/(partialx^2) = f_(xx) (2) (partial^2f)/(partialxpartialy) = f_(xy) (3) (partial^3f)/(partialx^2partialy) = f_(xxy). (4) Such partial...