A

David

Darling

partial derivative

The partial derivative is the ordinary derivative of a function of two or more variables with respect to one of the variables, the others being considered constants. If the variables are x and y, the partial derivatives of f(x, y) are written δf/δx and δf/δy, or Dxf and Dyf, or fx and fy. The partial derivative of a variable with respect to time is known as the local derivative.