The two aspects of the norm – orthoepy (the study of the standard phonemic structure of the word) and orthophony (the study of standard realisation of phonemes). Current orthoepic and orthophonic differences between the pronunciation of Muscovites and Petersburgers. Cooperation between the norm and the spoken and written language (views of Yevgeny Polivanov and Lev Shcherba). The diachronic limit of the language system. Norm evolution standards – first and second type variation.