Nation state
A nation state, or nation-state, is a political entity in which the state (a centralized political organization ruling over a population within a territory) and the nation (a community based on a common identity) are congruent. A nation, sometimes used in the sense of a common ethnicity, may include a diaspora or refugees who live outside the nation-state; some dispersed nations (such as the Roma nation, for example) do not have a state where that ethnicity predominates.