Abstract
Slavic and Baltic show a curious way of overt definiteness marking by means of a specific type of adjective inflection. It arose when the adjective merged with a definiteness marker of pronominal origin. This paper aims at a comprehensive explanation of the rise of the definite adjective morphology in the former branch. First of all, it is argued that contrary to what has been claimed, there is no need to posit loss of trapped morphology to plausibly account for the definite adjective inflection. It can be explained by a series of well-established processes, i.e., sound change, reanalysis, and analogy. An interplay of these processes led to an increase in the phonological fusion of the adjective and the definiteness marker and ultimately resulted in their merger. In discussing the involved changes and in identifying factors that may have motivated them, the paper contributes to the general study of how new inflectional morphology emerges from the coalescence of two formerly independent elements.