prototype (n.)

A term used in SEMANTICS and PSYCHOLINGUISTICS for a typical member of the EXTENSION of a referring expression. For example, a sparrow would be a prototype of bird, whereas an ostrich (because of its atypical characteristics, notably its inability to fly) would not. The notion has been particularly fruitful in studies of child language ACQUISITION, where it has been used to help explain the order of emergence of complex sets of related LEXICAL items, such as types of chair, drinking utensil or vehicle. Prototype semantics involves the development of criteria for the definition of prototypical meaning, with particular reference to the way that the ‘radial set’ of overlapping meanings interrelate, and the nature of category membership and boundaries.