This volume is based on edited papers presented at the Language and Space Workshop: Defining Functional and Spatial Features, held at the University of Notre Dame, South Bend, IN in June 2001. As we discuss in the introductory chapter, the goal of the conference was to examine how the concepts of ?feature? and ?function? and ?functional feature? are defined across the domain of cognitive science (including development, categorization, perception, and spatial language), and to assess the applicability of these definitions for defining features in language and space. The Notre Dame workshop was the second in a series, preceded by the ?Defining Direction in Language and Space: Axes and Vector Representations?, held in Lincoln, UK in 2000, and followed by ?Defining Granularity in Language and Space?, held in Bielefeld, Germany, 2002. We thank the Graduate School, the Institute for Scholarship in the Liberal Arts, the Department of Psychology, and the College of Arts and Letters Dean?s office, all at the University of Notre Dame, for funding for the conference. We thank John Davey, editor at Oxford University Press for his support and guidance during the editing process.