Peace is an elusive concept with many different meanings. Traditionally, it has been equated with the absence of war or violence, but such “negative peace” has limited value as it lumps wildly disparate situations together, such as rivalries (India–Pakistan) and close political relationships (e.g., European Union). Nevertheless, this conception remains the predominant approach in theory, research, teaching, and policy discourse. “Positive peace” definitions are much broader and encompass aspects that go beyond war and violence, but there is far less consensus on those elements. Conceptions include, among others, human rights, justice, judicial independence, and communication components. Best developed are notions of “quality peace,” which incorporate the absence of violence but also require things such as gender equality in order for societies to qualify as peaceful. Many of these, however, lack associated data and operational indicators. Research on positive peace is also comparatively underdeveloped. Peace can also be represented as binary (present or not) or as a continuum (the degree to which peace is present). Peace can be applied at different levels of analysis. At the system level, it refers to the aggregate or global conditions in the world at a given time. At the dyadic or k‑adic level, it refers to the state of peace in relationships between two or more states. Finally, internal peace deals with conditions inside individual states, and the relationships between governments, groups, and individuals. Aspects of peace vary according to the level of analysis, and peace at one level might not be mirrored at other levels.