a data structure in which a record is linked to two successor records, usually referred to as the left branch when greater and the right when less than the previous record.

a binary tree where each node has a Comparable key (and an associated value) and the key in any node is larger than the keys in all nodes in that node's left subtree and smaller than the keys in all nodes in that node's right subtree.

The subtree corresponding to the root node is the entire tree; the subtree corresponding to any other node is called a proper subtree. and consists of all the nodes below on the branch

The degree of a node in a network (sometimes referred to incorrectly as the connectivity) is the number of connections or edges the node has to other nodes.