Gradient

The derivative of a function with multiple variables.

It is a vector that points in the direction of a functions steepest increase. Its magnitude represents the maximum rate of change.

$$\nabla f(x_1,x_2,\dots ,x_n)=\left[\begin{array}{c}\frac{\partial f}{\partial x_1}\\ \frac{\partial f}{\partial x_2}\\ ⋮\\ \frac{\partial f}{\partial x_n}\end{array}\right]$$