The term Greek Orthodox may refer either to the Orthodox Church as a whole or to the various churches of the traditionally Eastern Roman ("Byzantine") lands.
In the English-speaking world, Greek Orthodox mainly refers to Orthodox Christians of ethnically Greek descent and the churches they inhabit. It is also used, however, to refer to all Orthodox Christians without regard to ethnicity, much as the term Roman Catholic is used to refer to all those who belong to the Roman Catholic Church, despite not being of Italian ancestry.
When used to refer to the churches of the Eastern Roman Empire, Greek Orthodox may include the Churches of Constantinople, Alexandria, Antioch, Jerusalem, Greece, Cyprus, Sinai, and Albania. In a number of cases, these churches may use the term Greek Orthodox to refer to themselves in English while in other languages using terms meaning other things, such as the Arabic Roum ("Roman").