Two notions of marginality are distinguished. The polycultural notion implies the existence of a boundary zone between cultural worlds. Its roots lie in Robert Park's notion of ‘marginal man’. The unicultural notion assumes a single referent culture that has a normative centre and a periphery to which the ‘social outcasts’ are relegated. This usage is common in the public and policy discourse and in studies of crime and poverty, for example in Loïc Wacquant's theory of regime of advanced marginality. Conceptual theory of metaphor is used to work out this distinction and to explore the metaphorical foundations of the concept, connecting it to the basic metaphor of society or culture as a bounded entity. The issue of margin is thematised as principal for the notion of marginality. These findings are discussed in the light of John Urry's and others' post-societal concepts of social and cultural life as well as Homi Bhabha's post-colonial notion of hybridity.