The defects of Sengor's definition on orogeny is discussed by means of analyzing the characteristics of orogenic belts. A new definition of orogenic belts is put forward. It involves the origins, characteristics and tectonic setting of orogenic belts. The old trichotomy scheme on orogenic belts is reviewed and a new one is presented to divide orogenic belts into three categories; intraplate, collision and subduction. The former classification of collisional orogens make it possible to put forward a new classification on collisional orogens that include four types: land-land collision, collision accretion, arc-land collision and non-mainland collision. The last one is a new type representing the early amalgamation processes of the crust.