Triforium

Triforium is derived from the Latin tres, tria 'three' and foris 'door, entrance'; its Greek equivalent is τρίθυρον, which originally referred to a building with three doors.

In the 15th-century churches in England, when the roof over the aisles was comparatively flat, more height being required for the clerestory windows, the triforium was dispensed with altogether.

In the great cathedrals and abbeys the triforium was often occupied by persons who came to witness various ceremonies, and in early days was probably used by the monks and clergy for work connected with the church.

When the flying buttress was frankly adopted by the Gothic architect and emphasized by its architectural design as an important feature, other cross-arches were introduced under the roof to strengthen it.

[9][page needed] In medieval churches, matronea lost their function of accommodation and became purely architectonic elements, placed over the side aisles with the structural purpose of containing the thrust of the central nave, and came to consist solely of bays so placed.