Definition:Tree (Graph Theory)/Leaf Node

Definition
Let $v$ be a node of a tree $T$.

Then $v$ is a leaf node of a $T$ iff $v$ 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 a terminal node, or just a leaf.

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.