A diaspora (from Greek διασπορά, "scattering, dispersion") is a scattered population whose origin lies within a smaller geographic locale. Diaspora can also refer to the movement of the population from its original homeland. Diaspora has come to refer particularly to historical mass dispersions of an involuntary nature, such as the expulsion of Jews from Judea, the fleeing of Greeks after the fall of Constantinople, the African Trans-Atlantic slave trade, the southern Chinese or Hindus of South Asia during the coolie trade, the Irish during and after the Irish Famine, the displacement of Palestinians in the 20th century, the exile and deportation of Circassians, and the emigration of Anglo-Saxon warriors and their families after the Norman Conquest of England, many of whom found employment in Constantinople and bolstered the elite bodyguard of the emperor, the Varangian Guard.
Recently, scholars have distinguished between different kinds of diaspora, based on its causes such as imperialism, trade or labor migrations, or by the kind of social coherence within the diaspora community and its ties to the ancestral lands. Some diaspora communities maintain strong political ties with their homeland. Other qualities that may be typical of many diasporas are thoughts of return, relationships with other communities in the diaspora, and lack of full integration into the host country.
The term is derived from the Greek verb διασπείρω (diaspeirō), "I scatter", "I spread about" and that from διά (dia), "between, through, across" + the verb σπείρω (speirō), "I sow, I scatter". In Ancient Greece the term διασπορά (diaspora) hence meant "scattering" and was inter alia used to refer to citizens of a dominant city-state who emigrated to a conquered land with the purpose of colonization, to assimilate the territory into the empire. An example of a diaspora from classical antiquity is the century-long exile of the Messenians under Spartan rule and the Ageanites as described by Thucydides in his "history of the Peloponnesian wars."