In computer science, a tree is a very common type of data structure. An ordered tree is a very common variety of tree, in which the children of each node of the tree are well-ordered. Thus, each node with children has a "first child", a "second child", and so on.

The ability to deal with each node's descendants in order is very important in many tree algorithms.

A particularly simple type of ordered tree is the binary tree, in which each node has two children, and we can ask for the "first child" and the "second child".

Trees (structure)