The article is devoted to determining the reasons for the differentiation of the conceptual and categorical apparatus of the branches of law, one of the manifestations of which is the differentiated content of the conceptual and categorical units “use” and “protection” of water resources in the context of different branches, and also to establishing a possible solution to this problem. The author outlines the main stages of formation of the conceptual and categorical apparatus of law, including in terms of differentiation of branches, which outline the specifics of formation of branch terminology systems in which a certain lexical unit may be used to denote similar, but not the same phenomena and processes as those for which it is used in the terminology systems of other branches of law. The author establishes that the first stage is the formation of the basic legal terminology, which is covered by the temporal period from the beginning of the development of the first social norms and ends with the stage of differentiation of branches of law. The second stage begins with the differentiation of branches of law and continues to the present day. It is characterized by the process of filling the universal legal terminology formed at the first stage with a new meaning within each branch of law, as well as the formation of branch-specific terminology systems. The third stage characterizes the current level and vector of development of legal terminology systems. It is concluded that differentiation of terminology in different branches of law, whereby some terms denote completely different in nature or, although similar, but different in essence legal phenomena and processes, impedes the effective formation of comprehensive mechanisms for legal regulation of the relevant relations. In addition, this state of affairs may reduce the effectiveness of law enforcement practice, hindering the formation of unified methods for resolving specific practical cases. It is determined that an important area for the development of natural resource law, as well as other branches of law, should be the development of terminology, in particular, in terms of its unification and universalization in order to avoid misinterpretations, to increase the efficiency of law enforcement practice and legal regulation of the relevant relations.