[tex]\nabla.\phi = \frac{\partial \phi_x}{\partial x} + \frac{\partial \phi_y}{\partial y}+\frac{\partial \phi_z}{\partial z}[/tex]
It looks like the dot product of [tex]\frac{\partial}{\partial x} +\frac{\partial}{\partial y} + \frac{\partial}{\partial z}[/tex] and [tex](\phi_x,\phi_y,\phi_z)[/tex].
It's an abuse of notation.
