This book is the first cross-linguistic study of clausal negation based on an extensive and systematic language sample. It examines the ways in which negation is expressed in the languages of the world from a new perspective and proposes a typological classification based on the structural differences between affirmative and negative clauses, the main types being symmetric and asymmetric negation. Cross-linguistic frequencies and correlations are also examined. It is argued that functional motivations of the different types of negation can be found in the functional differences between affirmation and negation. The book is of interest to language typologists, descriptive linguists and to all linguists interested in negation.