Applying the Nabla operator to a scalar field \(f\) results in a vector field (gradient field) with three components. At a point \((x,y,z)\) the vector \(\nabla \, f(x,y,z)\) points in the direction of the largest increase of \(f\).
Here \(\nabla\) is the Nabla operator. This is a vector operator with which vectorial derivatives like gradient, divergence or rotation can be formed.
A function depending on three coordinates \(x\), \(y\) and \(z\), which must be differentiable. For example: \( f(x,y,z) = x^2 + 5yz + z \).