The present article proposes a typology of the main varieties of uncertainty considered by economists and refines existing concepts. This typology combines three distinctions, between: substantive and procedural uncertainty; weak and strong uncertainty; and ambiguity and fundamental uncertainty. These concepts refer, or fail to refer, to factors such as: a lack of information; complexity; the (im)possibility of building probability distributions that are unique, additive and reliable; structural change; etc. When refining these concepts, the article pays special attention to the conception of social reality underlying each concept. It refers to what each concept may imply about the complexity and changeability of social reality and the limitations and creative potential of the individuals that inhabit this reality, in addition to, in some cases, the roles of institutions and the features of the process of technological change.453621640