notes concept of tree tree is set of one or more nodes such that there is specially designated node called rootand remaining nodes are partitioned into > disjoint set of nodes ,tn each of which is tree shown below in figure is structurewhich is tree figure tree structure this is tree because it is set of nodes {abcdefghi}with node as root nodeand the remaining nodes are partitioned into three disjoint sets{bghi}{cefand {drespectively each of these sets is tree individually because each of these sets satisfies the above properties shown below in figure is structurewhich is not treefigure non-tree structure this is not tree because it is set of nodes {abcdefghi}with node as root nodebut the remaining nodes cannot be partitioned into disjoint setsbecause the node is shared given below are some of the important definitionswhich are used in connection with trees degree of node of treethe degree of node of tree is the number of sub-trees having this node as rootor it is number of decedents of node if degree is zero then it is called terminal node or leaf node of tree degree of treeit is defined as the maximum of degree of the nodes of the treei degree of tree max (degree (node ifor to level of nodewe define the level of the node by taking the level of the root node to be and incrementing it by as we move from the root towards the sub-trees the level of all the descendents of the root nodes will be the level of their descendents will be and so on we then define depth of the tree to be the maximum value of level for node of tree lovely professional university