The article analyzes the use of the phrase language situation (linguistic situation) in diffe rent national scientific traditions and approaches to describing the language situation in Slavic countries. It was found that, despite the similarity of the general definitions of this concept, in specific studies the attention is mainly focused on one of three possible aspects — the relationship between the functioning of various idioms within society, the situation with the use of a certain idiom in a certain territory or in a certain community or on the intra- language proper situation, that is, the internal differentiation of language to meet the va- rious needs of society. The choice of research direction is determined primarily by the con- figuration of the language situation itself, i.e., whether it is endo- or exogenous, whether the state language has an established literary tradition and traditions of stylistic differentia- tion, a powerful dialect base, how widespread it is outside the range of the main distribu- tion of the language, etc. Ukrainian society is characterized as being in the process of transformation from an exogenous (characterized by mass bilingualism) to a predominantly endogenous (predomi- nance of the Ukrainian language) language situation. In this regard, there is a great need for research related to the analysis of language behavior of persons who are on the path of changing language preferences. Against the background of active migration processes pro- voked by the war, the problem of language adaptation of previously Russian-speaking citi- zens in a new language environment for them and the functioning of the Ukrainian lan- guage outside of Ukraine (as a diaspora and foreign language) becomes especially important. Given the limited possibility of making statistically reliable quantitative measurements of the language situation, the importance of studying individual language biographies of persons who have changed or are changing their language behavior is increasing. Keywords: language situation, language behavior, language policy, Slavic countries, language functioning, language corpus planning, majority language, minority language, Ukrainian lan- guage abroad.