This article examines negative language transfer in the use of Serbian prepositional constructions by Polish-speaking students of Slavic philology learning Serbian as a foreign language. The study aims to identify the most frequent interference-induced errors, analyse them contrastively, and indicate ways of preventing them becoming ingrained. The research material comprises a corpus of homework assignments and tests collected over fifteen years of teaching Serbian at different proficiency levels, supplemented with exercises designed for the study, particularly tasks involving the translation of sentences from Polish into Serbian. The material is examined through qualitative error analysis and a contrastive approach, with particular attention to semantic and syntactic differences between Polish and Serbian prepositional constructions. The analysis shows that Polish interference is manifested primarily in the selection of prepositions and the use of inappropriate case forms.
The largest group of errors involves constructions governing the accusative and genitive cases. While some
of the errors merely violate linguistic norms, others alter the intended meaning and may result in communicative
misunderstandings. The findings demonstrate the need for systematic comparison of structures in the two languages and for the use of varied contrastive, grammatical, and translation exercises from the initial stages of language instruction.
