\begin{definition}[Definition:Labeled Tree for Propositional Logic/Along a Branch]
Let $\left({T, \mathbf H, \Phi}\right)$ be a labeled tree for propositional logic.
Let $\Gamma$ be a branch of $T$.
Let $\mathbf A$ be a WFF that is attached to a node $t \in \Gamma$.
Then '''$\mathbf A$ occurs along $\Gamma$'''.
This includes the case where $\mathbf A \in \mathbf H$, that is, $\mathbf A$ is attached to the root node.
\end{definition}