Intra-linguistic Diglossia as a Special Kind of Folk Bilingualism on the Example of the Lechitic Languages

The interaction of several varieties of the same national language may, on the one hand, affect the dominance of the state language over ethnolects, which may eventually lead to their disappearance, and on the other hand, due to the evolutionary linguistic and cultural proximity, contribute to their preservation. The purpose of the study is to consider the form of existence of subsystems of the national language, namely languages characterized by limited territory and spheres of use and the official language. The Lechitic language community reflects a special kind of multilingualism - diglossia, this is the hypothesis of the study. The study analyzes the history of scientific research in the field of linguistic and cultural interactions between the Lekhite ethnoses, examines phonetic and grammatical similarities and differences of languages, as well as the centuries-old unity of the sociality of the Lechites. Using the example of the Kashubian regional language, common in the northern part of Poland, used in conjunction with the state Polish language, the intra-linguistic features of the Lechitic languages are determined, and the importance of the extralinguial approach for the of unofficial languages is emphasized. It is concluded that in the case of unbalanced bilingualism, the identified structures of the language pair, as well as the development of regionalism and cultures of ethical groups contribute to the preservation of unofficial languages.