The portico in front of ancient churches; sometimes, the atrium or outer court surrounded by ambulatories; -- used, generally, for any vestibule, lobby, or outer porch, leading to the nave of a church.
1. arcaded transverse porch or vestibule forming the entrance space of a basilica-style church. 2. covered antechamber at the main entrance of a church (usually, at the west end of the axis).. 3. a long, usually arcaded, porch forming an entrance into a public building
The narthex of a church is the entrance or lobby area, located at end of the nave, at the far end from the church's main altar. Traditionally the narthex was a part of the church building, but was not considered part of the church proper. It was either an indoor area separated from the nave by a screen or rail, or an external structure such as a porch.