Apse - Rounded and usually of a chancel or chapel.
Arcade - Row of arches, free-standing and supported on piers or columns; a blind arcade is a "dummy".
Arch - Can be round-headed, pointed, two-centered, or drop; ogee - pointed with double curved sides, upper arcs lower concave; lancet - pointed formed on an acute-angle triangle; depressed - flattened or elliptical; corbelled - triangular, peaked, each stone set a little further in until they meet, with a large capstone.
Arrow Loop - A narrow vertical slit cut into a wall through which arrows could be fired from inside.
Ashlar - Squared blocks of smooth stone neatly trimmed to shape.
Aumbry - Recess to hold sacred vessels; typically in a chapel.
Bailey - The ward or courtyard inside the castle walls, includes exercise area, parade ground, emergency corral
Baluster - A small column.
Balustrade - A railing, as along a path or stairway.
Barbican - The gateway or outworks defending the drawbridge.
Bar hole - Horizontal hole for timber bar used as a door-bolt.
Barrel vault - Cylindrical roof.
Bartizan - An overhanging battlemented corner turret, corbelled out; sometimes as grandiose as an overhanging gallery; common in Scotland and France.
Bastion - A small tower at the end of a curtain wall or in the middle of the outside wall; solid masonry projection; structural rather than inhabitable.
Batter - A sloping part of a curtain wall. The sharp angle at the base of all walls and towers along their exterior surface; talus.
Battlement - Parapet with indentations or embrasures, with raised portions (merlons) between; crenelations; a narrow wall built along the outer edge of the wall walk for protection against attack.
Bay - Internal division of building marked by roof principals or vaulting piers.
Belvedere - A raised turret or pavillion.
Berm - Flat space between the base of the curtain wall and the inner edge of the moat; level area separating ditch from bank.
Bivalate - A hillfort defended by two concentric ditches.
Blockhouse - Small square fortification, usually of timber bond overlapping arrangement of bricks in courses (flemish, dutch, french, etc.)
Murder Holes - A section between the main gate and a inner portcullis where arrows, rocks, and hot oil can be dropped from the roof though holes. Provides good cover for defenders and leaves the attacker open. Only used when outer gate has been breach.
Nailhead - Pyramid moulding.
Narthex - Enclosed passage between the main entrance and nave of a church; vestibule.
Nave - Principal hall of a church, extending from the narthex to the chancel.
Necking - Ornament at the top of a column, bottom of the capital.
Newel - Center post of spiral staircase.
Nookshaft - Shaft set in angle of jamb or pier.
Offset - Ledge marking the narrowing of a wall's thickness.
Oilette - A round opening at the base of a loophole, usually for a cannon muzzle
Olite - Granular limestone.
Open joint - Wide space between faces of stones.
Oratory - Private in-house chapel; small cell attached to a larger chapel.
Order - One of a series of concentric mouldings.
Oriel - Projecting window in wall; originally a form of porch, usually of wood; side-turret.
Orillons - Arrowhead bastions.
Oubliette - A dungeon reached by a trap door; starvation hole
Outer Curtain - The wall the encloses the outer ward.
Outer Ward - The area around the outside of and adjacent to the inner curtain.
Palisade - A sturdy wooden fence usually built to enclose a site until a permanent stone wall can be constructed.
Palmette - Looped like a palm-leaf.
Parados - Low wall in inner side of main wall.
Parapet - Low wall on outer side of main wall.
Pediment - Low-pitched gable over porticos, doors, windows.
Peel - A small tower; typically, a fortified house on the border
Pellet - Circular boss.
Perpendicular - English architectural style (1330-1540).
Petit appareil - Small cubical stonework.
Pier - Support for arch, usually square.
Pilaster - Shallow pier used to buttress a wall.
Pinnacle - Ornamental crowning spire, tower, etc.
Piscina - Hand basin with drain, usually set against or into a wall.
Pitch - Roof slope.
Pitching - Rough cobbling on floor, as in courtyards.
Plinth - Projecting base of wall.
Portcullis - A heavy timber or metal grill that protected the castle entrance and could be raised or lowered from within the castle. It dropped vertically between grooves to block passage or barbican, or to trap attackers.
Postern Gate - A side or less important gate into a castle; usually for peacetime use by pedestrians
Prow - Acute-angled projection.
Puddled - Made waterproof.
Putlog - Beams placed in holes to support a hoarding; horizontal scaffold beam
Putlog Hole - A hole intentionally left in the surface of a wall for insertion of a horizontal pole.
Quadrangle - Inner courtyard.
Quirk - V-shaped nick.
Quoin - Dressed stone at angle of building.
Rampart - Defensive stone or earth wall surrounding castle.
Rath - Low, circular ringwork.
Ravelin - Outwork with two faces forming a salient angle; like in a star-shaped fort.
Rear-arch - Arch on the inner side of a wall.
Redoubt - Small self-contained fieldwork, a refuge for soldiers outside the main defenses.
Reeded - Parallel convex mouldings.
Re-entrant - Recessed; opposite of salient.
Refectory - Communal dining hall.
Relieving arch - Arch built up in a wall to relieve thrust on another opening.
Respond - Half-pier bonded into a wall to carry an arch.
Retirata - Improvised fieldwork to counter an imminent breach.
Revetment - Retaining wall to prevent erosion; to face a surface with stone slabs.
Rib - Raised moulding dividing a vault.
Ringwork - Circular earthwork of bank and ditch.
Roll - Moulding of semi-circular section.
Romanesque - The prevailing architectural style, 8-12th cent.; massive masonry, round arches, small windows, groin-and barrel-vault.
Roofridge - Summit line of roof.
Rubble - Fill; unsquared stone not laid in courses.
Rustication - Worked ashlar stone with the faces left rough.
Salient - Wall projection, arrowhead.
Saltire - Diagonal, equal-limbed cross.
Sally-port - Small heavily fortified side door from which the defenders can rush out, strike, and retire.
Scaffolding - The temporary wooden frame work built next to a wall to support both workers and materials.
Scale - Carving resembling overlapping fish scales.
Scallop - Carved in a series of semi-circles.
Scappled - Cut to a smooth face.
Scarp - Slope on inner side of ditch.
Segmental - Less than a semi-circle.
Set back/off - Ledge on wall face.
Shaft - Narrow column.
Shell-keep - Circular or oval wall surrounding inner portion of castle; usually stores and accommodations inside the hollow walls.
Sill - Lower horizontal face of an opening.
Sleeper - Lowest horizontal timber (or low wall).
Soffit - Underside of arch, hung parapet, or opening.
Solar - Upper living room , often over the great hall; the lord's private living room.
Spandrel - Area between top of a column or pier and the apex of the arch springing from it.
Splay - Chamfer, or sloping face.
Spring - Level at which the springers (voussoirs) of an arch rise from their supports.
Squint - Observation hole in wall or room.
Stepped - Recessed in a series of ledges.
Steyned - Lined (like in a well).
Stockade - Solid fence of heavy timbers.
Stringcourse - Continuous horizontal moulding on wallface.
Tau cross - Plain T cross with equal limbs.
Tooth-in - Stones removed (or omitted) to allow another wall to be bonded into it.
Tracery - Intersecting ribwork in upper part of window.
Transom - Horizontal division of window; crossbar.
Trefoil - Three-lobed.
Truss - A timber frame used to support the roof over the great hall.
Tufa - Cellular rock; porous limestone.
Turning bridge - A drawbridge that pivots in the middle.
Turret - Small tower, round or polygonal; usually a lookout.
Tympanum - Space between lintel and arch over doorway.
Vault - Stone roofing.
Vitrified - Material reduced to glass by extreme heat.
Volute - Spiral scroll at angle of a capital.
Voussoir - Wedge-shaped stones in arch.
Wall-plate - Horizontal roof-timber on wall-top.
Wall-stair - Staircase built into the thickness of a wall.
Wall-walk - Passage along castle wall; may be roofed.
Water-leaf - Plain broad leaf moulding.
Wattle - A mat of woven (willow) sticks and weeds; used in wall and dike construction.
Wave - Sinuous moulding.
Weathering - Sloping surface to throw off rainwater.
Wicket - Person-sized door set into the main gate door.
Wing-wall - Wall downslope of motte to protect stairway.