Binary tree
In computer science
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...

, a binary tree is a tree data structure
Tree (data structure)
In computer science, a tree is a widely-used data structure that emulates a hierarchical tree structure with a set of linked nodes.Mathematically, it is an ordered directed tree, more specifically an arborescence: an acyclic connected graph where each node has zero or more children nodes and at...

 in which each node has at most two child nodes, usually distinguished as "left" and "right". Nodes with children are parent nodes, and child nodes may contain references to their parents. Outside the tree, there is often a reference to the "root" node (the ancestor of all nodes), if it exists. Any node in the data structure can be reached by starting at root node and repeatedly following references to either the left or right child.

Binary trees are used to implement binary search tree
Binary search tree
In computer science, a binary search tree , which may sometimes also be called an ordered or sorted binary tree, is a node-based binary tree data structurewhich has the following properties:...

s and binary heap
Binary heap
A binary heap is a heap data structure created using a binary tree. It can be seen as a binary tree with two additional constraints:*The shape property: the tree is a complete binary tree; that is, all levels of the tree, except possibly the last one are fully filled, and, if the last level of...

  • A directed edge refers to the link from the parent to the child (the arrows in the picture of the tree).
  • The root node of a tree is the node
    Node (computer science)
    A node is a record consisting of one or more fields that are links to other nodes, and a data field. The link and data fields are often implemented by pointers or references although it is also quite common for the data to be embedded directly in the node. Nodes are used to build linked, often...

     with no parents.