In Romanesque an Gothic Christian abbey, cathedral basilica and church architecture, the nave is the central approach to the high altar. "Nave" (Medieval Latin navis, "ship,") was probably suggested by the keel shape of its vaulting. The nave of a church, whether Romanesque, Gothic or Classical, extends from the entry — which may have a separate vestibule, the narthex — to the chancel and is flanked by lower aisles separated from the nave by an arcade. If the aisles are high and of a width comparable to the central nave, the structure is sometimes said to have three naves.