Is the root node an internal node?

Question

So I\'ve looked around the web and a couple of questions here in stackoverflow here are the definition:

• Generally, an internal node is any node that is not a leaf

Answer 1

"A node with no children is a leaf or external node. A non-leaf node is an internal node."

Source: "Introduction To Algorithms-3rd edition" page number 1176, last line.

So, root is also an internal node except when it is the only node of the tree.