Corbelled turret, square or round, frequently at an angle.
Bar tracery
A form of tracery introduced c. 1250, in which patterns are formed by intersecting moulded ribwork continuing upwards from the mullions. It was especially elaborate during the Decorated period of English Gothic, i.e. c. 1290-c. 1400.
Bascule
Hinged part of a lifting (or bascule) bridge.
Base
Moulded foot of a column or pilaster. An Attic base is the form used on an Ionic column, with two large convex rings joined by a spreading convex moulding.
Base cruck
A type of timber construction in which curving paired members (blades) rise from ground level to a tie-beam or collar-beam which supports the roof timbers.
Basement
Lowest, subordinate storey; hence the lowest part of a classical elevation, below the piano nobile or principal storey.
Basilica
A Roman public hall; hence an aisled building, especially a church, with a clerestory, i.e. windows in the walls rising over the aisles.
Basket arch
A three-centred and depressed arch, or one with a flat centre; also called anse de panier (French, lit. basket handle).
Bastion
One of a series of defensive semicircular or polygonal projections from the main wall of a fortress or city.