-> A graph G with n vertices is a Tree, then it has (n-1) edges.

1) Tree
2) Forest
3) Minimally Connected Graph
4) Spanning Tree
5) Minimum Spanning Tree
6) Prims's Algorithm
7) Kruskal's Algorithm
8) Binary Tree

n= Total No. of Vertices;
k= Total no. of Pendant Vertices;
m= Total no. of Internal Vertices;
e= Total no. of Edges

=> n = k+m
=> k = (𝑛+1)/2
=> m = n-k
=> e = n-1