What is “a transept” in a church?

In a cruciform church, the transept is the lateral arm that intersects the nave at the crossing, creating the familiar cross-shaped plan. Usually divided into north and south arms, it often contains side altars or chapels and provides circulation space for processions and pilgrims. Developed from early Christian basilicas and emphasized in Romanesque and Gothic architecture, the transept had both symbolic and practical roles—evoking the Crucifixion and allowing larger congregations to gather near relics. Its gable ends frequently carry grand portals or rose windows, and the junction with the nave is often marked by a tower or dome. For contrast: the nave is the long central space, the choir/chancel lies near the altar, and the narthex is the entry porch.