In cognitive linguistics, polysemy is regarded as a categorizing phenomenon; i.e., related meanings of words form categories centering around a prototype and bearing family resemblance relations to one another. Under this view, the scope of investigation has been gradually broadened from categories in the lexical and lexico-grammatical domain to morphological, syntactic, and phonological categories. The papers in this volume illustrate the importance of polysemy in describing these various categories. A first set of papers analyzes the polysemy of such lexical categories as prepositions and scalar particles, and looks at the import of polysemy in frame-based dictionary definitions. A second set shows that noun classes, case, and locative prefixes constitute meaningful and polysemous categories. Three papers, then, pay attention to polysemy from a psychological perspective, looking for psychological evidence of polysemy in lexical categories.