In this Master's thesis, I attempt to capture the disparate semiosis of two musical genres - a traditional opera, Rusalka, which has a unique position in Czech national music, and a musical of the same name. On the basis of theoretical findings from semiotics as a science, from the approaches of F. de Saussure, C. S. Peirce and R. Barthes, and by means of semiotic analysis, the thesis unravels semantic elements that are specific for theatrical art. Attention is directed at the symbol as a major tool for semiosis and the classification of symbols on the basis of Peirce's three ontological categories. The analysis focuses on decoding the semiotic systems used in the two genres (the libretto, the music, the characters, the story, and the technical and symbolic means that are employed). The analysis also deals with the question of intertextuality and the ideological background of the text, and attempts in this way to compare the differences and/or the similarities of diverse semiotic codes of the same class, and to capture their originality and specificity. At the same time, the thesis is focused on the dominant semiotic code of the two genres. This is, on the one hand, determined by the systemic distinctions between opera and musical theatre, while, on the other hand, it is primarily predetermined by...