\begin{definition}[Definition:Center of Tree]
Take a tree, and remove all the nodes whose degree is $1$, along with all their incident edges.
Repeat the process until either:
:One node is left
or:
:Two nodes are left, joined by a single edge.
If one node is left, it is called the '''center''' of the tree.
If two nodes are left, joined by a single edge, this is called the '''bicenter''' of the tree.
\end{definition}