The paper is an introduction to contemporary theoretical discourse about theatre adaptations. The phenomenon of staging texts and other sources of non-dramatic nature in the theatre developed mainly in the second half of the 19th century and in the 20th century, periods of increased interest in adaptation are cyclically recurring. The latest wave of staging of epic texts (and other) could have been observed in the seasons of the past decade in the Slovak theatre as well, but the theatrology has been dealing with this phenomenon rather marginally. The author attempts to create a basic landscape of the theory of adaptation in the international context, as well as in the domestic environment and points out the controversies that are being brought up in this area of research within the establishing field of adaptation studies. The second part of the paper deals with the question of adequate terminology and considers discrepancies in terminology proposed by various authors within the context of historical-philosophical bases and other social sciences (e.g. translatology). The paper presents a wide range of possibilities that theorists have come up with in order to clarify the conceptual apparatus for thinking about adaptations.