Informal organization refers to a small group the members of which are tied to one another as persons. The group is characterized by informal and face to face relations, mutual aid, cooperation and companionship.The members of informal organizations work together not in their official capacities but as persons. They share their hopes and fears, their joys and sorrows. The informal organizations consist of only rules and not statuses. Here there is no authority but only leadership.
Informal organizations have their own unwritten norms of behavior. They have their own ways of correcting and punishing the violators of the norms. Though they are smaller in size they give strength to the formal organizations to function effectively. These informal organizations resemble Cooley's Primary Groups and Sunmer's in –groups.