What Is Tree Terminology in Data Structure?


Heather Bennett

In the field of data structure, tree terminology refers to a set of concepts and terms used to describe the various elements and relationships within a tree data structure. Understanding these terms is essential for analyzing, designing, and implementing tree-based algorithms effectively.


A tree is a hierarchical data structure consisting of nodes connected by edges. It is composed of a collection of nodes, where each node contains a value and can have zero or more child nodes.


A node is an individual element in a tree that holds a value. Each node may also have references or pointers to its child nodes. A node without any children is called a leaf node, while a node with at least one child is called an internal node.


The root is the topmost node in a tree. It serves as the starting point for traversing the entire tree structure. A tree can have only one root.

Parent and Child Nodes

A parent node is any node that has one or more child nodes connected to it. Conversely, child nodes are those directly connected to their parent node.

Sibling Nodes

Sibling nodes are nodes that share the same parent. In other words, they are children of the same parent node.

Ancestor and Descendant Nodes

An ancestor node of a given node refers to any parent or grandparent (or higher-level ancestor) on the path from the root to that particular node.
On the other hand, a descendant node of a given node refers to any child, grandchild (or lower-level descendant) on the path from that particular node to any leaf node.


A subtree is a portion of a tree data structure composed of a node and its descendants. It can be considered as an independent tree itself.

Depth and Height of a Node

The depth of a node in a tree is the number of edges from the root to that particular node. The depth of the root node is always 0.
The height of a node in a tree is the number of edges on the longest path from that particular node to any leaf node.

Binary Tree

A binary tree is a specialized type of tree data structure in which each parent can have at most two children, typically referred to as the left child and right child.

Balanced Tree

A balanced tree, such as an AVL tree or red-black tree, is one in which the heights of subtrees differ by at most one level. This property ensures efficient operations and reduces search time within the tree structure.

In Conclusion

The understanding of these fundamental tree terminologies provides a solid foundation for comprehending more advanced concepts and algorithms related to trees. By familiarizing yourself with this terminology, you’ll be able to effectively navigate, analyze, and manipulate data within various types of trees.

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