This article is an attempt to address the subject of polysemy and synonymy in the terminological systems of English and Romanian languages. It is well known that terminological units are words, i.e. terms that have an exact reference in the source language, and their translation are committed to focus on the same dimension in the target language. Yet, this desideratum is not fully respected, this is due to the fact that the terminology is subject to the phenomenon of very active polysemy and synonymy. The factors related to this occurrence are many, nevertheless we consider that the most important feature of the synonymy and polysemy is that new terms are coined form already existing words via different means as suffixation, agglutination, change in the meaning, etc. The research below is an effort to classify the types of synonyms and their influence on the incidence of polysemy. The purpose of this research is to detect the cases of polysemy and synonymy by bringing examples of translation into Romanian and Russian and to give translators practical advice in order to avoid the pitfalls stretched by the phenomena described in the study that we have conducted.