There are a large number of opinions in literature about the essence, forms, and mechanism of diplomacy. This article presents a systematization of all definitions of diplomacy, an analysis of the conceptual evolution so far. According to contemporary investigators, diplomacy must be approached through the prism of science and art. The similarity of diplomacy with art is reached by identifying past definitions and current critical analysis. The correlation between diplomacy and diplomatic negotiations shows the idea that in their time international relations are managed and regulated, which determines diplomacy as an institution of power. From the point of view of the theory of international relations and international law, diplomacy ensures the efficient functioning of the international system, based on the principles and provisions of international treaties.