This chapter develops the book’s conceptual and terminological basis. It proposes to re-discover supranationality as a relative and general concept which can serve as a valuable descriptive-analytical tool for the study of international regimes and law beyond the state. Supranationality is defined by adopting a functional perspective: The chapter argues that elements usually denoted supranational seek a form of legal integration, either horizontally, through international institutions bypassing states in their ability to determine the legal position of individuals, or vertically, in that law beyond the state is entrenched in the domestic legal order in a way that allows individuals to rely on it directly. As a thin conceptual theory renouncing any broader normative vision, the proposed framework may complement and inform more fully-fledged theories such as legal pluralism, global constitutionalism or federalism. The chapter also explores the nexus between the notions of supranationality and community. Drawing on constructivist insights, it demonstrates that the constitution of a (legal) community in the sense of an intersubjective sense of belonging can be regarded both the (social) precondition and product of legal integration.