What is the root of a tree (root)?

The root is the top node of a tree, the one the entire structure starts from.

Characteristics:

• The root has no parent.
• All the other branches of the tree extend from it.
• From the root you can reach any other node by moving down along the edges.

Example:

Here A is the root of the tree.

Features:

• A tree always has exactly one root.
• If the root is removed, the tree splits into separate subtrees.
• In recursive structures (for example, in search), the work almost always starts at the root.

Summary: The root is the entry point into a tree, the main node from which all the other elements of the structure grow.