Hypostyle: having the roof beams supported on columns.
[I]mpluvium: the cistern sunk in the Atrium (which see) of a Roman house to receive the rain water.
Impost: the member above the capital of a column, on which the arch rests, usually composed of mouldings.
In Antis: See Portico.
Ionic: the order of architecture, developed by the Hellenes of Asia Minor and adjoining islands, and borrowed and modified by the mainland Hellenes.
Insula: Roman term for a residential building, housing many families.
Intercolumniation: specifically in Classic architecture, the space between any two columns, or between a column and the wall of the Cella.
Interlace: in decoration, an ornament composed of interwoven bands or lines.
[J]ambs: the side members of the openings of doors and windows.
[K]aaba: the cube-like shrine in the Mosque of Mecca.