The gradient

The gradient, whose old symbol is ``grad'', is the vector function of position obtained by applying the del operator to a scalar function $f(x,y,z)$. Thus, the gradient of $f$ is the vector:

$$\boxed{ \mathrm{grad} f = \nabla f \triangleq \hat{x} \frac{\part... ...hat{y} \frac{\partial f}{\partial y} + \hat{z} \frac{\partial f}{\partial z} }$$ (2.4)

By convention, the gradient of a scalar function is not underlined, even though it is a vector.