Dialectology is the study of language variation. Traditionally, this has largely been the province of dialect geographers, who concentrated on the speech of the linguistically conservative rural population in order to map regional differences. Interest has shifted to urban speech, and sociolinguists have correlated linguistic variables with other variables such as age, social class, sex and ethnic background. Dialectology not only provides a thorough exposition of these two approaches - their histories, methodologies and significant results, drawn from studies of a wide range of languages - it also integrates them within a single conceptual framework as two aspects of the same discipline. The authors argue that dialectology can thus make an important contribution to general linguistic theory and in particular answer questions about variability in language, which has in the past too often been assigned peripheral or accidental status. Designed primarily as a comprehensive textbook for undergraduate courses in dialect studies, this book also points towards innovative and stimulating research areas.