I will present the first results in construction of a lexicographic model of core chemical terms in French, English and Russian. FRONTERME is an interdisciplinary project on the terminology of chemistry carried out at the ATILF and the LPCT CNRS laboratories (Nancy, France). The project is aimed at the rigorous formal modeling of the core vocabulary of chemistry and of its interaction with the general language lexicon. In our study, we propose a non-ontological graph structuring of the lexicon by means of Lexical Systems. Using a multilingual perspective, we place high emphasis on connections between terms and non-terms, as well as on connections between interdisciplinary terms and on discrepancies between three languages. One of our main concerns is writing lexical definitions of chemical terms avoiding definitional ambiguities and proposing clearly structured and harmonized definitions of terms in French, English and Russian which will become an efficient tool for the understanding of scientific texts, for teaching chemistry and for scientific writing