Virtually all psychological theories of word meaning , as well as many theories of meaning developed in linguistics and philosophy, have focused on describing the nature of the concepts associated with words. For instance, psychologists have been concerned with issues such as whether the knowledge involved in knowing the meaning of bird or chair is better described as a set of defining features, a prototype, or representations of individual exemplars (e .g . , Smith & Medin , 1981), and whether the knowledge includes information about correlations between features (e.g . , Malt & Smith, 1984; Medin, Altom, Edelson, & Freko, 1982), beliefs about missing features (e .g . , Malt , 1990; Medin & Ortony, 1989; Smith, Medin , & Rips , 1984), or other types of nonfeatural information (e .g . , Murphy & Medin , 1985; Rips, 1989). This emphasis on studying the concepts associated with words , in traditional terminology, constitutes an interest in the intension. or semantic component, of word meaning.