Partial Derivative

For a function of more than one argument, the derivative with respect to one of them whilst treating the others as constants. Written as
\[ \frac{\partial f}{\partial x} \]
For example, the partial derivative of
\[ f(x, y) = x^2 y \]
with respect to \(x\) is
\[ \frac{\partial f}{\partial x} = 2 x y \]
as opposed to
\[ \frac{\mathrm{d}f}{\mathrm{d}x} = 2 x y + x^2 \frac{\mathrm{d}y}{\mathrm{d}x} \]
as determined by the product rule.