Paris became the largest city in the Western world during the thirteenth century, and has remained influential ever since. This book examines the interlinked history of Parisian speech and the Parisian population through various phases of immigration, dialect-mixing and social stratification from the Middle Ages to the present. It reveals how new urban modes of speech developed during periods of expansion, how the city's elites sought to distinguish their language from that of the masses, and how a working-class vernacular eventually emerged with its own "slang" vocabulary.