The "common core" of different sociolinguistic schools includes a number of general problems such as the social differentiation of language, the sociolinguistic aspects of bilingualism and diglossia, the typology of linguistic situations, language engineering, national and standard languages and their social functions, etc. Still urgent to the sociolinguists of all countries and all trends is the problem of developing their own methodology and the application of research methods developed by other disciplines to sociolinguistics. The above-mentioned problems constitute the major thrust of this book. It is not merely a summary of studies by a certain sociolinguistic school or even several schools; the main goal of the author is to elucidate a number of major philosophical and theoretical questions, fundamental problems of sociolinguistics and methods of sociolinguistic analysis.