1 Abstract The dissertation Theoretical tools for categorization and functional explanations of relations in language is focused on linguistic categorization from the perspective of empirical gram- matical research. The primary aim is to present the theoretical and practical potential for the investigation of grammatical categories, stressing functional explanations of why cer- tain language structures are the way they are. The text is divided into two parts. (i) The first two chapters are devoted to the theoretical and methodological foundations of empirical linguistic research (including issues of metalanguage, language comparison, discreteness and gradience). Particular emphasis is placed on functional-evolutionary approaches, which describe grammar in interconnection with language use, and more specifically on func- tional explanations by means of frequency. (ii) In the following three chapters, the potential of corpus-based research is demonstrated in accordance with the principles adopted in (i). It is applied to the linguistic categories of possession and adjective comparison in Czech. Possession in Czech is described with regard to hypotheses based on statistical tendencies in language use. The main results of the research revealed the relationship between frequency of use and the animacy hierarchy,...