\begin{definition}[Definition:Bound Occurrence]
Let $\LL_1$ be the language of predicate logic.
Let $\mathbf A$ be a WFF of $\LL_1$.
Let $Q x$ be an occurrence of a quantifier in $\mathbf A$.
Any occurrence of the variable $x$ in the scope of $Q$ is called a '''bound occurrence'''.
\end{definition}