Tree-Diagram Definitions o The circles in a tree diagram are called vertices or nodes o The top of the tree is called its root o the vertices immediately below a given vertex are callled the children of that vertex The(unique vertex immediately above a given vertex is called its parent. The root is the only vertex in the tree that has no parent 分支 ◆Th兄第 ting a vertex with one immed ately above or below is called a branch. 9 Siblings are vertices with the same parent.Tree-Diagram Definitions  The circles in a tree diagram are called vertices or nodes.  The top of the tree is called its root.  The vertices immediately below a given vertex are called the children of that vertex. The (unique) vertex immediately above a given vertex is called its parent. (The root is the only vertex in the tree that has no parent.) The line connecting a vertex with one immediately above or below is called a branch. Siblings are vertices with the same parent. 分支 兄弟