This book addresses the problems of the nature of the category of aspect its formal expression and its relation to Action modes to the AoristImperfect and PerfectNonPerfect distinctions. The discussion is largely based on data from Bulgarian a Slavonic language where aspect as a grammatical category systematically coexists not only with verbal prefixation but also with temporal boundedness correlation and in the nominal sphere definiteness. Crosslanguage parallels with English and French data and the mapping of Bulgarian structures to notions drawn from the western tradition of aspectual study result in the outline of a framework for an integrated study of the expression of aspectuality in languages belonging to different language groups.