\begin{definition}[Definition:Magnitude]
The '''magnitude''' (or '''size''') of a quantity (either vector or scalar) is a measure of how big it is.
It is usually encountered explicitly in the context of vectors:
If $\mathbf v$ is the vector quantity in question, then its '''magnitude''' is denoted:
:$\size {\mathbf v}$
or
:$v$
\end{definition}