The word diocese is derived from the Greek term διοίκησις meaning "administration". When now used in an ecclesiastical sense, it refers to a territorial unit of administration. In the Western Church, the district is under the supervision of a bishop (who may have assistant bishops to help him or her) and is divided into parishes under the care of priests; but in the Eastern Church, the word denotes the area under the jurisdiction of a patriarch and the bishops under his jurisdiction administer parishes. This structure of church governance is known as episcopal polity.