In computer science, a binary tree is a tree data structure 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 trees and binary heaps.

Note that this terminology often varies in the literature, especially with respect to the meaning of "complete" and "full".

in a perfect binary tree can be found using this formula: Failed to parse (Missing texvc executable; please see math/README to configure.): n = 2^{h+1}-1 where Failed to parse (Missing texvc executable; please see math/README to configure.): h is the depth of the tree.

in a complete binary tree is at least Failed to parse (Missing texvc executable; please see math/README to configure.): n = 2^{h} and at most Failed to parse (Missing texvc executable; please see math/README to configure.): n = 2^{h+1}-1 where Failed to parse (Missing texvc executable; please see math/README to configure.): h is the depth of the tree.