transept

In churches, the transept is a transverse body, inscribed within the perimeter of the building or projecting outwards, which is inserted between the presbytery area and the naves.
It derives from the Latin words trans , meaning beyond, and saeptum , meaning enclosure. The transept intersects the longitudinal nave at right angles and gives the church its classic Greek or Latin cross layout. The point of intersection, called the cross, is often covered by a dome and, in some cases, a spire with a drum.