Gradient
Let $f:{\mathbb{R}}^{n}\to \mathbb{R}$ be a scalar field. The gradient is
$$\nabla f\left(x\right)=\left[\begin{array}{c}\frac{\mathit{\partial}f}{\mathit{\partial}{x}{1}}\ \vdots \ \frac{\mathit{\partial}f}{\mathit{\partial}{x}{n}}\end{array}\right]$$