This chapter defines and contextualises the key concepts central to analysing Iranian identity: ethnicity, nationalism, solidarity, and pluralism. It elaborates on sociological categories such as mechanical and organic solidarity, relative deprivation, and institutional inequality. The chapter also discusses the religious and ethnic composition of Iran, using data such as the GAMAAN 2020 survey to demonstrate the pluralistic yet hierarchical nature of Iranian society. By linking these empirical realities to theoretical debates, it identifies the mechanisms through which religious and ethnic divisions are transformed into discursive conflicts. This chapter ultimately establishes the conceptual basis for subsequent empirical and analytical discussions.