The Greek noun diaspora means a dispersion or scattering — the condition of being scattered abroad. It became the technical term for Jewish communities living outside the land of Israel, and later for the universal Church dispersed throughout the nations.
The concept of diaspora is theological: Israel was scattered as judgment (Deuteronomy 28:25) but also positioned as witnesses among the nations. Peter addresses his letter 'to God's elect, exiles scattered (diaspora) throughout the provinces' (1 Peter 1:1), applying diaspora language to the Church. Believers are, in a profound sense, always in diaspora — sojourners on earth, citizens of heaven, present among the nations as ambassadors of the Kingdom.