The relationship between the principle of legal certainty and res judicata

The article discusses the concept of "res judicata" and "principle of legal certainty" in order to clarify their relationships. Whereas the term "res judicata" is known in the context of formulary process, the author refers to Roman law on the matter at hand. As in modern interpretation, “res judicata" is mentioned in the judicial practice of the European Court of Human Rights and the Constitutional Court of the Russian Federation, in this article there are citations to the judicial acts of these courts. As a result of reviews of scientific opinions of "res judicata" and the principle of legal certainty, the analysis of judicial practice and a brief historical reference to Roman law, the author concludes that there is a definitive interdependence of the studied concepts on the one hand, and the lack of identity, synonymity, on the other hand. The principle of legal certainty is the broader concept; "res judicata" is the starting idea for one of its aspects.