Imperial Roman administration
Originally eparchy (ἐπαρχίᾱ, eparchia) was the Greek equivalent of the Latin term provincia, one of the districts of the Roman Empire. As such it was used, chiefly in the eastern parts of the Empire, to designate the Roman provinces. The term eparch (Greek: ἔπαρχος, eparchos) however, designating an eparchy's governor, was most usually used to refer to the praetorian prefects (singular in Greek: ἔπαρχος τοῦ πραιτωρίου, "eparch of the praetorium") in charge of the Empire's praetorian prefectures, and to the Eparch of Constantinople, the city's urban prefect.
The Dominate-period administrative system was retained In the Byzantine period of the Empire until the 7th century. As Greek became the Empire's main administrative language, replacing Latin, in the latter 6th century even the provinces of the Exarchate of Ravenna, in reconquered Italy, were termed eparchiae in Greek as well as in Latin.
In the latter half of the 7th century, the old provincial administration was replaced by the thematic system. Even after that however, the term eparchos remained in use until the 840s for the senior administrative official of each thema, under the governing strategos. Thereafter, eparchs are evident in some cases as city governors, but the most important by far amongst them was the Eparch of Constantinople, whose office had wide-ranging powers and functioned continuously until the 13th century.
Modern Greece and Cyprus
The term eparchia was revived as one of the administrative sub-provincial units of post-Ottoman independent Greece, the country being divided into nomoi ("Prefectures"), of which in turn some were subdivided into eparchies. From 1887, the eparchies were abolished as actual administrative units, but were retained for some state services, especially finance services and education, as well as for electoral purposes. Before the Second World War, there were 139 eparchies, and after the war, with the addition of the Dodecanese Islands, their number grew to 147. The provinces were abolished in the mainland (but retained for the islands), in the wide-ranging administrative reform implemented in 1997 (the "Kapodistrias plan") and replaced by enlarged municipalities (demoi).
In Cyprus, the term eparchia is used to refer to the Districts of Cyprus.