Oecus

''Oecus'' is the Latinized form of Greek ''oikos'', used by Vitruvius for the principal hall or salon in a Roman house, which was used occasionally as a triclinium for banquets.

When of great size it became necessary to support its ceiling with columns; thus, according to Vitruvius, the tetrastyle ''oecus'' had four columns; in the Corinthian ''oecus'' there was a row of columns on each side, virtually therefore dividing the room into nave and aisles, the former being covered over with a barrel vault. The Egyptian ''oecus'' had a similar plan, but the aisles were of less height, so that clerestory windows were introduced to light the room, which, as Vitruvius states, presents more the appearance of a basilica than of a triclinium.

Vitruvius distinguishes four types of oecus:

# Tetrastylos: with four columns; # Corinthian: with a row of columns supporting an architrave topped with a cornice and a vaulted ceiling; # Egyptian: particularly magnificent form of the ''oecus'', with columns running all around, which support a gallery also provided with columns; # Cycicene (κυζίκηνοι from Cyzicus, an ancient city in Mysia): a very spacious, north-facing garden ''oecus'' common among the Greeks. Provided by Wikipedia