If several cases are related to each other, the Civil Procedure Code provides for procedural arrangements, including the merger or consolidation of litigation, in order to prevent the issuance of conflicting judgments as well as to increase the quality and efficiency of the proceedings. Accordingly, in this research, first, in simple terms, the semantics orConceptology of the relationship between lawsuits and criteria and how to achieve it has been investigated. This has been considered with the approach of comparative law and according to the international guidance texts of civil procedure law and its comparison with domestic laws. According to the study of the issue in domestic and comparative law, it seems that the criteria of connection between the claims and their insignificant differences are a subsidiary issue in this subject, and the focus is on the substantive connection of common or closely related interests under consideration, which will be examined by the court as a substantive matter. According to the results mentioned, in interpreting the rules, providing solutions to issues, as well as future amendments to the rules of procedure, enhance the managerial power of the judge in order to examine the status of the relation between the claims and their effects and issue an appropriate order in this regard should be given more attention to the course of the proceedings.