The present research is concerned with the problems aimed at the role of the Thraco-Dacian substratum in the formation of the Romanian language. Most languages have been influenced at some time or other by contacts, resulting in various transfer degrees of features from one to another. A substratum language is one that was used before a new language arrived and took it over. B. P. Hasdeu is the founder of such research in the Romanian linguistics. According to him the substratum is one of two elements of the „primary mixture”;for Romanian these are Latin and Thraco-Dacian.