In the middle of the ninth century, the recently Christianised Slavic peoples entered into literature and history through the offices of two Byzantine missionaries, the Thessalonian brothers Constantine-Cyril and Methodius, who, having invented a new alphabet, proceeded to translate sacred and liturgical texts. This book traces the progress of this event, which has had a profound influence on Slavic culture, crystallising its mentality and determining the evolution of the modern national languages, particularly that of Russian. It recounts the genesis, the transformations and the functions of palaeoslavic within the mediaeval Slavic world, providing an accurate phonetic, morphological and syntactic description of the language, complete with numerous examples and morphological tables.