The Turkic language family features a wealth of expressions of modality, with large inventories of items within individual languages and considerable cross-linguistic variation. Taking the hierarchy of scope between different modal classes and their link to neighboring categories as a starting point for a basic classification, the study focuses on the internal semantic subdivision of three major classes of modality together with representative formal expressions of the semantic classes from numerous modern and pre-modern Turkic languages. The evolution of particular forms and underlying abstract structure types and their dissemination throughout the Turkic languages are investigated as well as the major semantic changes that can be observed in diachrony. The paths of conventionalization identified within Turkic are compared against universal paths of grammaticalization documented in the linguistics literature.§This comprehensive synchronic and diachronic survey identifies the common basic parameters of Turkic modality systems, provides an insight into the intra- and cross-linguistic diversity, and offers new perspectives for further research into this hitherto little-studied domain. ukryj opis