Social group or category of the population that, in a larger society, is set apart and bound together by common ties of language , nationality, or culture .
Ethnic diversity, the legacy of political conquests and migrations, is one aspect of the social complexity found in most contemporary societies. The nation-state has traditionally been uneasy with ethnic diversity, and nation-states have often attempted to eliminate or expel ethnic groups. Most nations today practice some form of pluralism , which usually rests on a combination of toleration, interdependence, and separatism. The concept of ethnicity is more important today than ever, as a result of the spread of doctrines of freedom, self-determination, and democracy. See also culture contact ; ethnic cleansing ; ethnocentrism ; race ; racism .