What Is Tree in Data Structure Simple Definition?


Larry Thompson

A tree is a widely used data structure in computer science that represents a hierarchical structure. It is composed of nodes connected by edges, where each node can have zero or more child nodes. The topmost node in the tree is called the root, and each child node can have its own children, forming subtrees.

Tree Terminology

Before we dive deeper into understanding trees, let’s familiarize ourselves with some key terminology:

  • Node: Each element in a tree is called a node. A node contains data and may have references to its child nodes.
  • Edge: An edge represents the link between two nodes.

    It connects a parent node to its child node(s).

  • Root: The topmost node in the tree is called the root. It does not have any parent nodes.
  • Child: A child node is directly connected to its parent node via an edge.
  • Parent: A parent node has one or more children connected to it via edges.
  • Sibling: Nodes that share the same parent are called siblings.
  • Leaf: A leaf node is a terminal node that does not have any children.

The Importance of Trees

Trees are essential data structures used in various applications due to their efficiency and versatility. They provide an organized way of storing and accessing data. Here are some common applications where trees are used:

  • Hierarchical Data Representation:
  • Trees are often used to represent hierarchical relationships, such as file systems, organization structures, and family trees. The parent-child relationship between nodes allows for easy navigation and organization of data.

  • Searching and Sorting:
  • Trees can be used to efficiently search for and retrieve data.

    Binary search trees, for example, allow for fast searching by dividing the search space in half at each step.

  • Decision Trees:
  • Decision trees are used in machine learning and artificial intelligence to make decisions or predictions based on input features. They provide a clear visualization of possible outcomes and help in decision-making processes.

  • Network Routing Algorithms:
  • Trees are employed in network routing algorithms to determine the shortest path between nodes or destinations. By organizing network connections in a tree-like structure, efficient routing can be achieved.

Types of Trees

Trees come in different variations based on their properties and characteristics. Here are some common types of trees:

Binary Trees

A binary tree is a type of tree where each node has at most two children: a left child and a right child. The left child is smaller than the parent node, while the right child is greater. Binary trees are commonly used for efficient searching and sorting operations.

Balanced Trees

A balanced tree is a type of tree where the heights of its subtrees differ by at most one level. Examples include AVL trees and Red-Black trees. Balanced trees ensure that operations such as insertion, deletion, and searching have optimal time complexity.

Binary Search Trees (BST)

A binary search tree (BST) is a binary tree where the values of all nodes in the left subtree are less than the value of the parent node, and the values of all nodes in the right subtree are greater. BSTs provide efficient searching and sorting capabilities.

Heap Trees

Heap trees are specialized binary trees that satisfy either the max-heap property or the min-heap property. In a max-heap tree, each parent node is greater than or equal to its child nodes, while in a min-heap tree, each parent node is less than or equal to its child nodes. Heap trees are commonly used in priority queues and heap sort algorithms.


Trees are fundamental data structures that play a crucial role in various applications. They provide an organized way of representing hierarchical relationships, enable efficient searching and sorting operations, aid in decision-making processes, and facilitate network routing algorithms. Understanding different types of trees and their properties is essential for designing efficient algorithms and data structures.

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