This article examines the note on languages in eleven philosophical courses taught in the Kyiv-Mohyla Academy in the seventeenth and eighteenth centuries. This small textual fragment, which discusses from which old languages newer languages came, is studied in the context of the Mohylian doctrine of signs, especially the question whether words are “natural” or “conventional” signs. The author provides a classification of the eleven courses under study and examines the textual differences between them. He also investigates the origin of the note, the ways in which it came to the Mohylians, and, most importantly, how Mohylian philosophical courses influenced each other. Finally, the author discusses the role of “lingua Ruthenica” and its place in the classification of languages developed by the professors of the Kyiv-Mohyla academy.