\begin{definition}[Definition:Rational Number]
A number in the form $\dfrac p q$, where both $p$ and $q$ are integers ($q$ non-zero), is called a '''rational number'''.
The set of all '''rational numbers''' is usually denoted $\Q$.
Thus:
:$\Q = \set {\dfrac p q: p \in \Z, q \in \Z_{\ne 0} }$
\end{definition}