Definition:Rooted Tree/Child Node/Grandchild Node

Definition
Let $T$ be a rooted tree with root $r_T$.

Let $t$ be a node of $T$.

A child of a child node of a node $t$ can be referred to as a grandchild node of $t$.

In terms of the parent mapping $\pi$ of $T$, a grandchild node of $t$ is a node $s$ such that:


 * $\pi \left({\pi \left({s}\right)}\right) = t$