The nave is the central part of a church, extending from the entrance to the altar. It is where the congregation gathers for worship.
The transept is a cross-shaped area that intersects with the nave, forming the arms of a crucifix.
The apse is a semicircular or polygonal space at the end of the nave, usually containing the altar.
Clerestory: The clerestory is an upper level of windows in a church's nave that allows natural light to enter.