Definition:Arborescence/Definition 2

Definition
Let $G = (V, E)$ be a directed tree.

That is, if the arcs of $E$ are replaced by edges, then the resulting simple graph is a tree.

Let $r \in V$.

Then $G$ is an arborescence of root $r$, an $r$-arborescence, or just an arborescence iff:


 * For each $v \in V$ there exists a directed path from $r$ to $v$.