transept

A transept is the arm of a cruciform church that projects at right angles from the main body of the building, creating the cross-shaped plan common in many Western cathedrals. The term derives from Latin transeptum, meaning “across a barrier.” In a typical layout, the transepts intersect the nave at the crossing, and together with the choir form the central axis of the church.

The transepts provide additional space beyond the nave, usually for chapels, altars, or seating, and they help organize ceremonial processions around the sanctuary. Architecturally, the transept bays may be tall and windowed, and the crossing above them is often emphasized with a tower, dome, or lantern. The presence and height of the transepts contribute to the silhouette and acoustics of the building.

Most churches with a cruciform plan have two transepts: a north transept and a south transept. Some buildings feature false transepts that project outward without forming a full arm, or have shortened transepts in later or more compact designs. In some architectural periods, transepts are elaborated with galleries or additional chapels along their lengths.

Transepts are a defining element of medieval European architecture and the broader cruciform church tradition, though not all church designs include them. They help distinguish a cross-shaped plan from a simple longitudinal layout and are often key to the building’s spatial organization and visual balance. Notable examples include Chartres Cathedral, Canterbury Cathedral, Notre-Dame de Paris, and Saint Sernin in Toulouse.