In the article, the content of the notions “term” and “term-synonym” in the scientific texts of the XVIII century is revealed. During the analysis of J. C. Gottsched’s works “Versuch einer Сritischen Dichtkunst” and “Vollständigere und neuerläuterte Deutsche Sprachkunst, nach den Mustern der besten Schriftsteller des vorigen und itzigen Jahrhunderts abgefasset”, absolute and relative synonyms have been singled out. As for structural features, it should be noted that the author described synonymous relations between simple, complex terms and terminological combinations. The article focuses on the motivated German terms, which are synonymous with the Latin ones.