Reciprocals are an increasingly hot topic in linguistic research. This reflects the intersection of several factors: the semantic and syntactic complexity of reciprocal constructions, their centrality to some key points of linguistic theorizing (such as Binding Conditions on anaphors within Government and Binding Theory), and the centrality of reciprocity to theories of social structure, human evolution and social cognition. No existing work, however, tackles the question of exactly what reciprocal constructions mean cross-linguistically. Is there a single, Platonic ‘reciprocal’ meaning found in all languages, or is there a cluster of related concepts which are nonetheless impossible to characterize in any single way? That is the central goal of this volume, and it develops and explains new techniques for tackling this question. At the same time, it confronts a more general problem facing semantic typology: how to investigate a category cross-linguistically without pre-loading the definition of the phenomenon on the basis of what is found in more familiar languages.