binary trees nodefor examplenodes and are the children of all nodes that have the same parent are known as siblingsbut there is no direct access between siblings thuswe cannot directly access node from node or vice versa nodes nodes that have at least one child are known as interior nodes while nodes that have no children are known as leaf nodes the interior nodes of the sample tree are shown with gray backgrounds in figure (band the leaf nodes are shown in white subtree tree is by definition recursive structure every node can be the root of its own subtreewhich consists of subset of nodes and edges of the larger tree figure shows the subtree with node as its root every node is the root of its own subtree figure subtree with root node relatives all of the nodes in subtree are descendants of the subtree' root in the example treenodes jrkand are descendants of node the ancestors of node include the parent of the nodeits grandparentits great-grandparentand so on all the way up to the root the ancestors of node can also be identified by the nodes along the path from the root to the given node the root node is the ancestor of every node in the tree and every node in the tree is descendant of the root node binary tree illustrations the trees illustrated above used directed edges to indicate the parent-child relationship between the nodes but it' not uncommon to see trees drawn using straight lines or undirected edges when tree is drawn without arrowswe have to be able to deduce the parent-child relationship from the placement of the nodes thusthe parent is always placed above its children with binary treesthe left and right children are always drawn offset from the parent in the appropriate direction in order to easily identify the specific child node note