Determines a designation system for styrene/acrylonitrile thermoplastic material, which may be used as the basis for specifications. The types of styrene/acrylonitrile plastic are differentiated from each other by a classification system based on appropriate levels of the designatory properties: a) melt flow rate b) Vicat softening temperature together with information about basic polymer parameters, intended application and/or procedure of processing, additives, fillers, important properties and reinforcing material.