This article arose from the need to comprehend, firstly, methodological and linguodidactic problems (by linguodidactics we understand the principles of language description for learning purposes) to mastering any non-native language, not only widespread foreign languages, and, secondly, from the need to comprehend not only the teaching of a second foreign language itself but also the content of training professionals of a second foreign language (students of universities and faculties of foreign languages). Theoretical and methodological problems associated with mastering any non-native language are especially acute when we are dealing not with the first, but with the second, third, etc. non-native language. This may be a second foreign language (for example, at school), a second foreign language as the language of a pedagogical specialty (for example, at a pedagogical university), the language of ethnic (self) identification (among members of national diasporas), etc. Therefore, in this paper, along with discussing general issues of mastering a non-native language, we focus on various situations of teaching a language as a second non-native.