# 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 *D*_{x}*f* and *D*_{y}*f*, or *f*_{x} and *f*_{y}. The partial derivative of a variable with
respect to time is known as the **local derivative**.