This volume contains a selection of the papers presented at the 16th International Symposium at the University of Wisconsin/Milwaukee. Two central question were addressed: What is the nature of the categories that underlie the structure of human language? What is the nature of extralinguistic categories that are reflected in language? These questions are addressed from the perspective of a variety of disciplines, using many different methodologies and focusing on many different aspects of language including morphology, syntax, semantics, phonology and discourse. The volume is divided into 3 sections: prototype effects in language, categorization processes, and cross-linguistic categorization.