One of the defining properties of a [[Vector]]. To get the magnitude of a vector, you can treat the vector's Cartesian coordinates as the $x$ and $y$ of a triangle. $\huge\parallel\vec{v}\parallel = \sqrt{ \vec{v}_{0}^{2} + \vec{v}_{1}^{2} + \cdots }$ Magnitudes are **never** negative $\huge\begin{align*} \let k &\in \R\\ \parallel k\vec{v} \parallel &= |{k}| \parallel \vec{v} \parallel \end{align*}$