(af (bh figure forest and its corresponding tree forest can also be defined as an ordered set of zero or more general trees while general tree must have roota forest on the other hand may be empty because by definition it is setand sets can be empty we can convert forest into tree by adding single node as the root node of the tree for examplefig (ashows forest and fig (bshows the corresponding tree similarlywe can convert general tree into forest by deleting the root node of the tree binary trees binary tree is data structure that is defined as collection of elements called nodes in binary treethe topmost element is called the root nodeand each node has or at the most children node that has zero children is called leaf node or terminal node every node contains data elementa left pointer which points to the left childand right pointer which points to the right child the root element is pointed by 'rootpointer if root nullthen it means the tree is empty figure shows binary tree in the figurer is the root node and the two trees and are called the left and right sub-trees of is said to be the left successor of likewiset is called the right successor of note that the left sub-tree of the root node consists of the nodes and similarlythe right sub-tree of the root node consists of nodes and in the treeroot node has two successors and node has two successor nodes and node has two successors and node has no successor node has two successor nodes and node has two successors and finallynode has only one successor binary tree is recursive by definition as every node in the tree contains left sub-tree and right sub-tree even the terminal nodes contain an empty left sub-tree and an empty right sub-tree look at fig nodes and have no successors and thus said to have empty sub-trees root node figure binary tree root node (level (level (level (level figure levels in binary tree terminology parent if is any node in that has left successor and right successor then is called the parent of and correspondinglys and are called the left child and the right child of every node other than the root node has parent level number every node in the binary tree is assigned level number (refer fig the root node is defined to be at level the left and the right child of the root node have level number similarlyevery node is at one level higher than its parents so all child nodes are defined to have level number as parent' level number degree of node it is equal to the number of children that node has the degree of leaf node is zero for examplein the treedegree of node is degree of node is zero and degree of node is sibling all nodes that are at the same level and share the same parent are called siblings (brothersfor examplenodes and nodes and nodes and nodes and and nodes and are siblings