binary tree binary tree consists of finite set of nodes that is either emptyor consists of one specially designated node called the root of the binary treeand the elements of two disjoint binary trees called the left subtree and right subtree of the root note that the definition above is recursivewe have defined binary tree in terms of binary trees this is appropriate since recursion is an innate characteristic of tree structures diagram binary tree binary tree terminology tree terminology is generally derived from the terminology of family trees (specificallythe type of family tree called lineal charteach root is said to be the parent of the roots of its subtrees two nodes with the same parent are said to be siblingsthey are the children of their parent the root node has no parent great deal of tree processing takes advantage of the relationship between parent and its childrenand we commonly say directed edge (or simply an edgeextends from parent to its children thus edges connect root with the roots of each subtree an undirected edge extends in both directions between parent and child