1. A Roman hall of justice, typically with a high central space lit by a {{clerestory}} and lower {{aisles}} all around it, and with {{apses}} or exedrae for the seats of the judges. 2. The form of the early Christian church, a central
high {{nave}} with {{clerestory}}, lower aisles along
the sides only, with a semicircular {{apse}} at the end. Often preceded by a vestibule ({{narthex}}) and {{atrium}}. In larger basilicas, there are often {{transepts}}, and sometimes five aisles. -- The Illustrated Dictionary of Historic Architecture