The doctoral thesis is an interdisciplinary study in applied linguistics, which examines contemporary linguistic theories in correlation with the development of foreign language didactics, also evaluating the traditions of the French language subject in Latvia. Linguodidactics is based on interdisciplinary research in linguistics and didactics on how to create a scientifically sound and conceptually structured language teaching system. The theoretical basis of the doctoral thesis research is formed by linguistic theories, which focus on the content of language as a subject, i.e. what to teach and learn; however, the focus of linguodidactics is the question of how to make the teaching and learning process more effective in relation to the purpose, tasks, methods, forms of learning organization and methodological techniques for the development of communicative, linguistic and sociocultural competence of the French language as a third language subject. The object of the research is the historical development of the French language as a third language in Latvia and the contextualization of theoretical findings in empirical research. The subject of the research is the principles of developing the content of French language teaching and its variability at the lexical-semantic learning level. The aim of the doctoral thesis is to characterize the content of French language teaching at the lexical-semantic level in the course of historical development in Latvia and, based on the theories of third language acquisition and psycholinguistics, to develop the principles of developing a concept of teaching French as a third language that meets the needs of Latvian students for the acquisition of lexical-semantic elements in secondary school. The scientific aspect of the research goal is to obtain a theoretical, scientifically based understanding of the process of lexical processing and acquisition in a third language. In turn, the practical aspect of the research goal is related to the improvement of the theory and practice of French language teaching, so that the experience gained in the study and the results summarized can be used to organize a French language teaching process that is appropriate to the situation in Latvia and meets the needs of students, implementing a plurilingual approach.