Placing the research in historical perspective, the article's main goal is to explicate systemic paradigmatic relations between words in Russian and Bulgarian. The typological and etymological affinity of Bulgarian and Russian is rooted in the shared linguistic and historical past and hence is the legitimate subject-matter of the research. The main hypothesis of the research is that despite the common ancestry, Russian and Bulgarian have developed along their own, unique ways, determined by both linguistic and extralinguistic causes. In the course of the languages' protracted and chequered history, centrifugal forces have dominated over the centripetal ones, as a result of which Bulgarian and Russian have emerged as typologically different languages. The common denominator, however, is that apart from having an extremely complex system of grammatical endings, Russian and Bulgarian also share a substantial number of formally and/or semantically overlapping words. The main research methods are systemic and stratified sampling, and contrastive-typological analysis. The results of the research have revealed a paradigm of crosslinguistic lexical relations, among which metonymy, synonymy, hyponymy, contrast, and cross-linguistic homonymy play a crucial role. The findings of the research are of interest to historical and synchronic linguistics and have linguodidactic value in that they make foreign language teaching and learning more explicit, conscious, and motivated.