This theoretical chapter explores the polymorphic, dynamic and contextual aspects of institutions. It proposes first a short literature review that addresses institutional pluralism. Three main approaches are distinguished: one that focuses on the social and institutional regulation of the economy, one that examines the existence of non-state legal norms and one that addresses the diversity of norms in their empirical expression. The main contributions of each approach are identified as are some of their limitations. This is followed by a review of the works that specifically deal with the ways in which different normative regimes interact. We argue that researchers rarely theorise these interrelations as such. Pointing to the necessity of constructing typologies of modes of interaction between normative systems, the chapter concludes by calling for empirical research to document the multiplicity of institutional forms made up of a large repertoire of norms that are constantly interacting and evolving.