The use of the same term with different meanings and the use of different terms with somewhat analogous meanings are not exceptional phenomena in scientific language. This article deals with polysemy and synonymy, and consists of three parts. The introductory part gives a brief description of the dictionaries and encyclopedias published up to the present time and justifies the choice of the examples in this case study, namely the polysemic term coherence and four synonymous couples of concepts and terms: documentary/instrumental translation, overt/covert translation and interlingual interpretive/interlingual descriptive communication as well as direct/indirect translation. The second part offers a comparison between the various dictionaries and encyclopedias and shows how the polysemic term coherence and the related pairs of concepts/terms are dealt with. It also indicates how the profusion of terminology could more effectively meet the needs of everyone who is engaged in translation and Translation Studies. The purpose of the third part is to demonstrate that in the training of translators, it is necessary to dispose of a metalanguage and that terminological diversity as a reflection of theoretic-conceptual diversity may be seen as an opportunity.