Definition:Tree (Graph Theory)/Leaf Node
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Let $v$ be a node of a tree $T$.
Then $v$ is a leaf node of a $T$ if and only if $v$ is of degree $1$.
If $T$ is a rooted tree, this is equivalent to saying that $v$ has no child nodes.
Also known as
A leaf node is also known as just a leaf.
In the context of rooted trees, a leaf node is often referred to as a terminal node.
In the context of more general graphs which are not trees, a degree $1$ vertex is known as a pendant vertex or an end vertex.
Consider the rooted tree below:
The leaf nodes are $2$, $4$, $6$, $8$ and $9$.
- Results about leaf nodes can be found here.
- 1979: John E. Hopcroft and Jeffrey D. Ullman: Introduction to Automata Theory, Languages, and Computation ... (previous) ... (next): Chapter $1$: Preliminaries: $1.2$ Graphs and Trees: Trees
- 1996: H. Jerome Keisler and Joel Robbin: Mathematical Logic and Computability ... (previous) ... (next): $\S 1.7$: Tableaus