Loop:- In general a n/w consist n nodes which are interconnected in some way by a branches then it is possible to transfer addjustance branches starting at any nodes in diffrant ways.Such a node path formed  by a network branches is known as loop. In other word loop is connected some graph of a connected graph such that at each node thier are two terminal made co-inside it may a loop pair ckt.

Properties of loop:- 
Thier are a exectaly two path b/w any pair of a node in the ckt.
Thier exist at least two branches in loop.
The maximum possible branches in a loop are equal to no. of nodes.