ETYM Late Lat., from Latin tri- (see Tri-) + foris, pl. fores, a door.
The gallery or open space between the vaulting and the roof of the aisles of a church, often forming a rich arcade in the interior of the church, above the nave arches and below the clearstory windows.
Gallery or arcade over an aisle; gallery over nave and choir.
Gallery over nave and choir.