Important Note: Although the del operator is a vector differential operator and we wrote it as a vector, it should be used with care since it is not a true vector (for instance, it does not have a magnitude). The reasons will become obvious later on but for now, the operator should only be used in the form given above. As an example, we have not defined (and, in fact, cannot define) the scalar or vector product between the del operator and other vectors or with itself. The extension of the considerations and notation given here to other coordinate systems should be avoided at this stage since all our discussion was in Cartesian coordinates. With this notation, the gradient of a scalar function is written as