The article highlights peculiarities of lexical complementarity of the terms in the German, English and Ukrainian languages in the term system of international relations. The terminological units of the above terminological sphere are analyzed and compared taking into consideration their internal and external forms. The dependence of internationalization of the term and its motivation on its lexical length is revealed. The obtained results show the degree of similarity of the terms of international relations in the studied languages, determining the possible prospects for their harmonization.