Merriam-Webster Collegiate Dictionary - diocese

 noun  (plural ~s)  Etymology: Middle English diocise, from Anglo-French, from Late Latin diocesis, alteration of dioecesis, from Latin, administrative division, from Greek dioikesis administration, administrative division, from dioikein to keep house, govern, from dia- + oikein to dwell, manage, from oikos house — more at vicinity  Date: 14th century the territorial jurisdiction of a bishop  • diocesan adjective