What Is Non Leaf Node in Data Structure?


Heather Bennett

In data structures, a non-leaf node is a fundamental concept that plays a crucial role in various hierarchical structures. To understand what a non-leaf node is, let’s first explore the concept of trees.

Trees and Nodes

A tree is a widely used data structure that represents hierarchical relationships between objects or elements. It consists of nodes connected by edges. Each node can have zero or more child nodes, except for the root node, which has no parent.

Nodes in a tree are classified into two categories: leaf nodes and non-leaf nodes.

Leaf Nodes

A leaf node, also known as an external node, is a node that has no children. In other words, it is the end point of a branch in the tree. Leaf nodes are usually represented as the final elements or entities in a hierarchical structure.

Example: Consider a file system where directories and files are organized in a hierarchical manner. In this case, individual files represent leaf nodes as they do not have any children.

Non-Leaf Nodes

A non-leaf node, also called an internal node or branch node, is any node within a tree that has one or more child nodes. These nodes serve as intermediaries connecting different parts of the tree.

Example: Continuing with the file system analogy, directories represent non-leaf nodes as they contain other directories and files within them.

Properties of Non-Leaf Nodes

Non-leaf nodes possess several important properties:

  • Parent Node: A non-leaf node always has at least one parent node above it. The parent node can be considered as its immediate predecessor in the tree hierarchy.
  • Child Nodes: Non-leaf nodes can have one or more child nodes branching out from them.

    These child nodes can be either leaf nodes or other non-leaf nodes.

  • Siblings: Sibling nodes are nodes that share the same parent node. Non-leaf nodes can have sibling nodes, which are also non-leaf nodes in this context.

Applications of Non-Leaf Nodes

Non-leaf nodes find extensive use in various data structures and algorithms:

  • Binary Trees: In binary trees, non-leaf nodes are essential for organizing and navigating through the structure efficiently. They allow for efficient searching, insertion, and deletion operations.
  • B-trees: B-trees are self-balancing search trees commonly used in databases and file systems.

    Non-leaf nodes in B-trees store keys as well as pointers to child nodes, enabling efficient data retrieval.

  • Trie: A trie is a tree-like data structure used for efficient retrieval of strings or sequences. Non-leaf nodes in a trie represent common prefixes shared by multiple strings.


In summary, a non-leaf node is a node within a tree data structure that has one or more child nodes branching out from it. It serves as an intermediary between different parts of the tree and plays a vital role in efficient data organization and traversal. Understanding the concept of non-leaf nodes is essential for mastering various hierarchical structures and their associated algorithms.

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