The article gives an account of research into the relationships that exist between varities of pluricentric languages, introducing central concepts and theoretical underpinnings of pluricentric research, covering power relationships, expressions of identity and attitudes as well as the debate on pluricentricity vis-à-vis pluriareality. The article surveys foundational work in the field concerning linguistic structural differences between varieties as well as more recent work on pragmatic  and interactional variation in pluricentric languages.