binary trees so they're not hard to remember figure shows many of these terms applied to binary tree root is the parent of and is the left child of the dashed line is path level level is the right child of subtree with as its root level level heijand are leaf nodes figure tree terms path think of someone walking from node to node along the edges that connect them the resulting sequence of nodes is called path root the node at the top of the tree is called the root there is only one root in tree for collection of nodes and edges to be defined as treethere must be one (and only one!path from the root to any other node figure shows non-tree you can see that it violates this rule figure non-tree