Aisle - space between arcade and outer wall.
Allure - also known as the wall walk, it is the path running behind the parapet at the top of a wall or tower.
Ambulatory - aisle round an apse.
Apse - rounded and usually of a chancel or chapel.
Arbalestina - cruciform loophole, used by crossbowmen.
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.
Arrow Slit - a vertical 'window', very narrow on the outside, spreading to a larger size one could stand in on the inside, out of which one shot, guess what, arrows. Later ones had a horizontal slot in the middle to give a wider angle of fire for crossbows.
Ashlar - squared blocks of smooth stone neatly trimmed to shape.
Aumbry - recess to hold sacred vessels; typically in a chapel.

Bailey - also known as the ward. The courtyard-like area of ground enclosed by a stone wall or wooden palisade, where the domestic buildings of the castle were. Includes exercise area, parade ground, emergency corral. In a concentric castle, the area between two encircling walls.
Bailiff - person in charge of allotting work to peasants, organising repairs to castles, and doing other jobs on a medieval castle.
Ballista - siege engine in the form of a large catapult.
Baluster - a small column.
Balustrade - a railing, as along a path or stairway.
Barbican - also called a hornwork. A structure built to protect the outside of an entrance. Can also be, as at Ludlow and Exeter, a special kind of towered gatehouse built in two parts. The gateway or outworks defending the drawbridge.
Bar hole - horizontal hole for timber bar used as a door-bolt.
Barmkin - the small walled yard attached to a pele tower (generally Scottish).
Barracks - building or group of buildings used to accommodate soldiers.
Barrel vault - cylindrical roof.
Bartizan - an overhanging battlemented corner turret, corbelled out; sometimes as grandiose as an overhanging gallery; common in Scotland and France. These are particularly notable in the castles of North Wales.
Base cruck - form of timber-framed construction where the roof is supported by curved timbers rising from the walls and not by aisle posts set on the floor
Basinet - close fitting medieval soldier's helmet, with a visor.
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.
Bastion Tower - tower projecting from the wall face and functioning as a bastion.
Bastle House - small tower house with a living room over a byre
Batter - also known as talus or plinth. A sloping part of a curtain wall. The sharp angle at the base of all walls and towers along their exterior surface; talus. Outward slope of a revetment.
Battery - grouping of artillery.
Battered Plinth - lovely jargon. This refers to the base of a wall being provided with a widening slope, both to strengthen the bottom of the wall against undermining and to provide a ricochet surface for objects such as rocks being dropped down from machicolations that would bounce off horizontally and zap the attackers.
Battering Ram - large beam used to break down the walls or doors of a fortification
Battlement - also known as crenellations. Crenellated parapet. Parapet with indentations or embrasures, with raised portions (merlons) between; 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.
Bay window - a window projecting out from a building at ground level, either rectangular or polygonal, of one or more storeys. A window that projects out from a building above ground level is known as an oriel window.
Belfry - tall, movable wooden tower on wheels, used in sieges.
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.
Billet - ornamental moulding used in Norman architecture, consisting of raised cylindrical or rectangual blocks at regular intervals.
Bivalate - a hillfort defended by two concentric ditches.
Blind arcade - line of arches on the face of a solid wall for decoration.
Blockhouse - small square fortification, usually of timber bond overlapping arrangement of bricks in courses (flemish, dutch, french, etc.).
Bond - arrangement of bricks in courses.
Bond tenant - a tenant who was bound to provide a labour service as part of his tenure; later changed to a money payment.
Bonnet - freestanding fortification; priest's cap.
Boss - central stone of arch or vault; key stone.
Bow - window as bay window but curved in plan.
Brattice or breteche - also known as hoarding. Timber tower or projecting wooden gallery; hoarding.
Breastwork - heavy parapet slung between two gate towers; defense work over the portcullis.
Bressumer - beam to support a projection.
Broch - drystone freestanding tower with interior court, no external windows (which face into the court), spiral stair inside wall, typically Iron Age Celtic refuge in Scotland.
Bulwark - bastion or (in first half of 16th century) a blockhouse.
Burg - German stronghold.
Burh - Saxon stronghold; literally a "neighborhood".
Buttery - from French bouteillerie, meaning storage room for beverages, next to the kitchen, a room from where wine was dispensed. The "Butler's" room off the Great Hall. Wine cellar, serving room, silverware, etc. See also Pantry (I'm not sure how the allocation of functions between the buttery and the pantry were differentiated - in Norman French/English buttery means 'bottle room' and pantry means 'bread room').
Buttress - wall projection for extra support; flying - narrow, arched bridge against the structure (usually employed for cathedrals); pilaster - gradually recedes into the structure as it ascends.

Cable moulding - a Norman moulding carved like a length of rope.
Camera - private room used for both living and sleeping, set apart from the more public areas of a house. Campshedding - facing of piles of boarding along a bank.
Cap-house - small chamber at the top of a spiral staircase in a tower or turret, leading to the open wall-walk on the roof .
Capital - distinctly treated upper end of a column. Capital the head of a pillar, often decorated.
Caponier - covered passage within a ditch.
Caponnière - covered passage across a ditch to an outer fortification structure such as a ravelin.
Carotid - heart-shaped.
Casemate - covered chamber for musketry or artillery.
Casemates - artillery emplacements in separate protected rooms, rather than in a battery.
Casement - bomb-proof vaulted accommodation for troops, stores or guns.
Castellan - officer in charge of a castle.
Catapult or Perrier - a stone throwing engine, powered by teams of soldiers pulling on ropes.
Cavalier - raised structure containing a batteru, usually sited above the centre of a bastion. Raising the battery gives a better trajectory.
Cesspit - the opening in a wall in which the waste from one or more garderobes was collected.
Chamfer - surface made by smoothing off the angle between two stone faces.
Chancel - the space surrounding the altar of a church.
Chemin de ronde - rare in England, very characteristic of French castles, this is the 'crown' at the top of a round tower, a machicolated gallery below or replacing the parapet. French castle towers also had conical roofs, but this was never common in England where they usually had flat tops.
Chemise wall - formed by a series of interlinked or overlapping semicircular bastions.
Chevron - zig-zag moulding.
Citadel - heavily fortified, independent defensive structure within city walls, dominating an ancient or medieval town; in the bastion system, the strongest part of the fort.
Choir - the part of a cruciform church east of the crossing.
Clasping - encasing the angle.
Cloister - four-sided enclosure with a covered walk along each side connecting a church with the principal administrative and domestic buildings.
Clunch - hard chalky material.
Cob - unburned clay mixed with straw.
Colonnade - range of evenly spaced columns.
Column - pillar (circular section).
Concentric - having two sets of walls, one inside the other.
Concentric - castle with two or more rings of defences, one inside the other.
Constable - official in charge of castle in owner's absence.
Coping - covering stones.
Corbel - a projecting block of stone built into a wall during construction; step-wise construction in order to support a roof beam or some other weight, as in an arch, roof, etc.
Corbiestepped or Crowstepped - squared stones forming steps upon a gable.
Corkscrew - a circular staircase - the most economical, if not the most convenient to use, method of accessing upper floors in a vertical tower; also, easier to defend.
Corinthian - elaborately foliated capital.
Cornice - decorative projection along the top of a wall.
Counterfort - defence work of besieging force.
Counterguard - a long, near-triangular freestanding fortification within the moat.
Counterscarp - outer slope of a ditch.
Course - level layer of stones or bricks.
Courtyard - walled enclosure in a castle.
Courtyard castle - type of castle consisting of a stone curtain wall that surrounds a courtyard, with buildings built inside the courtyard, normally against the curtain wall.
Couvre Face - low rampart in the ditch, protecting the face of a ravelin; analogous in function to the counterguard and fausse braye.
Covered Way - protected communication all round the works of a fortress on the outer edge of a ditch, covered by earthworks from enemy fire. Passage along the outer edge of a ditch, protected by a rampart forming the glacis; it is usually some 10 metres wide.
Crannog - celtic Scotland timber-built fortified lake village.
Creasing - shaped mark on a wall, marking the pitch of a former roof.
Crenel - the low segment of the alternating high and low segments of a battlement.
Crenelation - also known as embattled. Battlements at the top of a tower or wall. Where a parapet is built with gaps (crenels) at regular intervals, allowing the defenders to shoot through the gaps and shelter behind the solid parts (merlons).
Crocket - curling leaf-shape.
Cross-and-orb - modified cross slits to accommodate gunnery.
Crossbow - weapon with a bow arranged at a right-angle to a wooden stock; it was used to fire metal bolts
Crosswall - interior dividing wall; structural.
Crow-steps step-gabled end to a roof. Also called corbie steps.
Crownwork - Freestanding bastioned fortification in front of main defenses.
Cunette - trench in the bottom of a ditch.
Cupola - hemispherical armored roof.
Curtain Wall - a connecting wall hung between two towers surrounding the bailey. Curtain wall the perimeter wall of a fortification, or any wall within a castle that does not support a roof and is used to link towers i.e. a wall 'hung' between towers.
Cushion - capital cut from a block by rounding off the lower corners.
Cusp - curves meeting in a point. Cusp a projecting point forming a leaf shape in the tracery of a gothic door-arch or window-head.
Cyclopean - drystone masonry, ancient, of huge blocks.

Daub - a mud of clay mixture applied over wattle to strengthen and seal it.
Dead-ground - close to the wall, where the defenders can't shoot.
Desmene - area of land reserved for a lord.
Diaper work - decoration of squares or lozenges.
Diaphragm - wall running up to the roof-ridge.
Dog-leg - a right angle in a passageway (for example, garderobes usually had a dog-leg approach so that the air from the privy pit would not blow back directly into the room).
Dog-legged - with right-angle bends.
Dog-tooth - diagonal indented pyramid. Zig-zag carving around an archway, typical of the Normans.
Donjon - a great tower or keep.
Dormer or Dormer window - window placed vertically in sloping roof.
Double-splayed - embrasure whose smallest aperture is in the middle of the wall.
Drawbridge - a heavy timber platform built to span a moat between a gatehouse and surrounding land that could be raised when required to block an entrance. Drawbridge wooden bridge that could be raised and lowered, sited in front of a tower or gatehouse, across a ditch. Everyone knows what a drawbridge is. There were basically three types: (1) a simple sliding platform over the ditch that could be pulled back, (2) a raising bridge pulled up by chains attached to the outer corners, and (3) a bridge with posts reaching out over the top, with the chains hanging vertically from the posts (this had 'leverage' advantages).
Dressing - carved stonework around openings.
Dripstone - a projecting moulding above an arch or lintel to throw off surface water.
Drum Tower - a large, circular, low, squat tower built into a wall.
Drystone - unmortared masonry.
Dubbing - ceremony in which a monarch or high ranking lord gives another person the title of knight; usually involving tapping each shoulder with a sword .
Dun or Dum - an Iron Age fortified enclosure, built of dry-stone, often with galleried walls, dating from the 1st century AD.
Dungeon - The jail, usually found in one of the towers.

E-plan tower house - tower house with a main block and at least two wings at right angles, dating from the 16th and 17th centuries.
Earthwork - fortification made of earth mounds, banks and ditches.
Eaves - the overhanging edge of a roof.
Embattled - battlemented; crenellated.
Embrasure - also known as crenel. The low segment of the altering high and low segments of a battlement. Embrasure - the space between merlons on a battlemented wall, also known as a crenel.
Enceinte a fortified enclosure Enceinte - The enclosure or fortified area of a castle.
Enclosure - castle courtyard.
Enfilade - describing the arrangement of Arrow Loops or Gun Ports whereby one could achieve a cross-fire and hit the enemy from the side.

Gable - wall covering end of roof ridge.
Gallery - long passage or room.
Garderobe - a small latrine or toilet either built into the thickness of the wall or projected out from it; projects from the wall as a small, rectangular bartizan.
Garret - the top storey of a building within the roof.
Garrison - the soldiers who manned and occupied a castle or fort.
Gate House - the complex of towers, bridges, and barriers built to protect each entrance through a castle or town wall.
Gauntlet - armoured glove, often with long cuff.
Glacis - a bank sloping down from a castle which acts as a defence against invaders; broad, sloping naked rock or earth on which the attackers are completely exposed. Rampart of the Cowered Way, sloping away towards the enemy. Featured in the song "The British Grenadiers"
Great chamber - Lord's solar, or bed-sitting room.
Great Hall - the building in the inner ward that housed the main meeting and dining area for the castle's residence; throne room. A great hall usually had a Solar, Buttery, Pantry, and kitchen attached to it.
Groined - roof with sharp edges at intersection of cross-vaults.
Groin - junction of two curved surfaces in a vault.
Gun-loop or gun-port opening in a wall for a gun.

Half-shaft - Roll-moulding on either side of opening.
Half-timber - The common form of medieval construction in which walls were made of a wood frame structure filled with wattle and daub.
Hall - Principal room or building in the castle complex.
Hall House - a defensible two-storey building containing a hall above a basement.
Hammerbeam - roof late-medieval form of roof supported on horizontal beams (hammerbeams) projecting from the walls; it enabled the central span of the roof to be open.
Heraldry - the system of coats of arms used to identify noble families.
Herringbone - brick or stone laid in alternate diagonal courses.
Herisson - a barrier of stakes, arranged randomly in the ground to prevent a direct approach from attackers.
Hillfort - Bronze or Iron Age earthwork defenses of concentric ditches and banks.
Hoarding - also known as brattice or breteche. A timber gallery built out at the top of a wall or tower, sometimes with a roof, which had doors in the floor through which one could drop offensive material upon or shoot arrows at one’s attackers . Sometimes built for permanence, of considerable size, and used as living quarters. Upper wooden stories on a stone castle wall; the living area; sometimes, a temporary wooden balcony suspended from the tops of walls from which missiles could be dropped.
Honour - large feudal estate, usually centred on a castle.
Hood - arched covering; when used as umbrella, called hood-mould.
Hornwork - freestanding quadrilateral fortification in front of the main wall. 'Horned' structure, consisting of two demibastions, one at each end of a curtain.

Impost - wall bracket to support arch.
Inner Curtain - the high wall the surrounds the inner ward.
Inner Ward - the open area in the center of a castle.
Iron Age - in Britain from c.600 BC to Roman period.

Jamb - side posts of arch, door, or window.
Joggled - keyed together by overlapping joints.
Joist - wall-to-wall timber beams to support floor boards.
Joust - combat, put on for entertainment, in which two knights rode towards each other with lances.
Justiciar - chief political and judicial officer under Noman and early Plantagenet kings.

Keep - also known as donjon. A strong stone tower; main tower; stronghold. Usually the strongest building in a castle.
Keystone - central wedge in top of arch.
Knight - man who served his lord as a mounted warrior.

L-plan tower house - distinctive Scottish form of the tower house in which a wing was added at right angles to the main tower block
Label - projecting weather moulding above a door or window to deflect rainwater.
Lancet - long, narrow window with pointed head.
Lantern - small structure with open or windowed sides on top of a roof or dome to let light or air into the enclosed space below.
Lattice - laths or lines crossing to form a network.
Lias - greyish rock which splits easily into slabs.
Light - glazing; component part of window, divided by mullions and transoms.
Lintel - horizontal stone or beam bridging an opening (window or portal).
Loggia - covered arcade or colonnade.
Longbow - large, powerful wooden bow, used to shoot arrows, often over long distances.
Loophole - narrow, tall opening, in a wall slit for light, air, or shooting through.
Lord - any male member of the nobility or knighthood, often holder of a castle or manor.
Louvre - opening in roof (sometimes topped with lantern) to allow smoke to escape from central hearth.
Lozenge - diamond shape.
Lunette - triangular (originally crescent-shaped) defensive structure, open at the rear, often flanking a ravelin.

Machicolations - projecting gallery on brackets, on outside of castle or towers, with holes in floor for dropping rocks, shooting, etc. The openings in the floor of a projecting stone gallery - a stone version of timber hoarding or breteche.
Mail or chain mail - flexible armour made of interlocking metal rings.
Mangonel - stone throwing catapult used as a siege engine.
Mantlet - detached fortification preventing direct access to a gateway; low outer wall.
Merlon - the high segment of the alternating high and low segments of a battlement. (Also see crenellated).
Meurtriere - an opening in the roof of an entrance passage where soldiers could shoot into the room below. Also see Murder Hole. Also, water could be poured down the meurtrière to extinguish any fires the enemy might set to destroy the door. Only used when outer gate has been breached.
Mezzanine - a low storey beween two higher ones (entresol).
Mine gallery - siegwork to call wall collapse.
Moat - a deep trench usually filled with water that surrounded a castle. A water-filled ditch around the perimeter of a castle, manor, settlement, etc., for defense.
Moline - ends curling outward.
Mortar - a mixture of sand, water, and lime used to bind stones together; as opposed to drylaid masonry.
Motte - a mound of earth on which a tower was built; artificial conical earth mound (sometimes an old barrow) for the keep.
Motte-&-bailey - commonly used phrase to describe a mound of earth with wood or stone keep, surrounded by ditched and palisaded enclosure (or courtyard).
Moulding - masonry decoration; long, narrow, casts strong shadows.
Mullion - vertical division of windows. The vertical divider of a window that's constructed in panels.
Multivallate - hillfort with three or more concentric lines of defence.
Mural - wall (adjectival). Having to do with a wall. A mural tower is a tower standing on a wall.
Mural stair - staircase built within the thickness of a wall.
Murder Hole - 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.
Neck Ditch - ditch cutting across a neck of land, to hinder an enemy's advance.
Necking - ornament at the top of a column, bottom of the capital.
Newel - center post of spiral staircase.
Niche - vertical recess in a wall, often to take a statue.
Nookshaft - shaft set in angle of jamb or pier.

Offset - ledge marking the narrowing of a wall's thickness.
Ogee - a double curve, bending one way and then the other.
Oilette - a round opening at the base of a loophole or arrowloop, usually for a cannon muzzle.
Olite or Oolite - granular limestone.
Onager - Roman name for a Mangonel, literally a "wild ass". A light stone throwing engine, powered by a skein of twisted rope.
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 (similar to a hoarding, but smaller); side-turret.
Orillons - Round or squared-off extensions of a bastion's faces, designed to protect its recessed flanks.
Oubliette - a dungeon reached by a trap door; starvation hole Oubliette dungeon or pit under the floor, reached by a trap-door, used for incarcerating prisoners.
Outer Curtain - the wall the encloses the outer ward. The outermost curtain wall within the shell wall; otherwise, the shell wall itself.
Outer Ward - The area around the outside of and adjacent to the inner curtain.

Page - young boy of noble birth who served the household of a lord, and sometimes became a squire.
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.
Pantile - a roof-tile of curved s-shaped section.
Pantry - associated with the Buttery in the Great Hall complex. I'm not sure what its function was as differentiated from the former. Pantry actually means 'bread room' (pan French equals bread). The lower end of a great hall, opposite the lord's dais at the upper end, almost always had three doors: buttery, pantry, and passage to kitchen.
Parados - low wall in inner side of main wall, edging the wallwalk.
Parapet - low wall on outer side of main wall, edging the wallwalk.
Pediment - low-pitched gable over porticos, doors, windows.
Peel - a small tower; typically, a fortified house on the border. Peel originally a palisaded court. Later a stone tower house.
Pele tower - isolated keep-like tower, built during the later Middle Ages in northern England, but more commonly in Scotland and Ireland.
Pellet - circular boss.
Pend - an open ended passage through a building, at ground level.
Perpendicular - English architectural style (1330-1540).
Perrier - a stone throwing engine, powered by teams of soldiers pulling on ropes.
Petit appareil - small cubical stonework.
Piatta Forma - fortification structure protecting the curtain between two bastions; it is square or rectangular in plan, or takes the form of a small tetrahedral bastion.
Pier - support for arch, usually square.
Pikeman - soldier carrying a pike or similar long-handled weapon.
Pilaster - shallow pier used to buttress a wall.
Pinnacle - ornamental crowning spire, tower, etc.
Pipe rolls - annual accounts of sheriffs rendered to the king.
Piscina - hand basin with drain, usually set against or into a wall.
Pitch - roof slope.
Pitching - rough cobbling on floor, as in courtyards.
Place of Arms - enlarged area in a covered way, where troops could assemble.
Plinth - also known as talus. 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. A wood and metal or metal gate, welded to form a giant grid that would slide down within the entrance of the gatehouse or hornwalk or barbican to reinforce the security of the door or to trap attackers.
Postern - a small secondary doorway in a tower or curtain wall, usually for peacetime use by pedestrians.
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.
Quatrefoil - four sided.
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 (basically, one of the points protruding from the fort).
Rear-arch - arch on the inner side of a wall.
Redan - outwork with two faces forming a salient angle.
Redoubt - small self-contained fieldwork, a refuge for soldiers outside the main defenses.
Reduit - detached, independent outwork.
Reeded - parallel convex mouldings.
Re-entrant - recessed; opposite of salient.
Reeve - peasant appointed as supervisor of work on the lord's land.
Refectory - communal dining hall.
Relieving arch - arch built up in a wall to relieve thrust on another opening.
Rere-arch - arch that supports the inner face of a wall above a door or window opening.
Respond - half-pier bonded into a wall to carry an arch.
Retirata - improvised fieldwork to counter an imminent breach.
Retrenchment - interior defence works, usually consisting of a trench and parapet.
Revet - face with a layer of stone for more strength. Some earth mottes were revetted with stone. Revetment - retaining wall to prevent erosion; to face a surface with stone slabs.
Rib - raised moulding dividing a vault.
Rib vaulting - arched roof with ribs of raised moulding at the groins.
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.
Roundel - low, circular, semicircular or U-shaped tower for artillery, projecting from the wall face.
Rubble - fill; unsquared stone not laid in courses. Stone construction using irregular stones imbedded in mortar.
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.
Screen passage - service passage screened off at the service end of a hall.
See - seat or area of authority of bishop or archbishop, also known as diocese.
Segmental - less than a semi-circle (e.g. segmental arch).
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. A keep built in the form of a high, circular or many-sided wall which encloses the area at the motte top and which has the domestic buildings adjoining the inside of the wall. The old motte-and-bailey castles were generally wooden stockades. As power was consolidated, the richer Norman lords built round stone walls on top of their mottes which were thus rendered fireproof. (At the same time, the Bailey curtain wall was also built up in stone.)
Shell wall - the wall itself, as above, without the interior buildings. The stores and accommodations might be within the shell’s hollow walls, or the walls might be solid stone and surround the donjon and various other freestanding buildings.
Sheriff - Royal official, based in a castle, who was in charge of law and order.
Shield Wall - exceptionally thick wall, protecting the castle on its most vulnerable side.
Shifting house - building where gunpowder is checked and prepared.
Shot-hole - hole for firearms, generally smaller than a gun-port .
Siege engine - large weapon or device, such as a battering ram or big catapult, used to attack a castle.
Siege tower - wooden tower on wheels which attackers used to climb over castle walls.
Sill - lower horizontal face of an opening.
Six-foil - six-lobed.
Sleeper - lowest horizontal timber (or low wall).
Slight - to damage or destroy a castle to render it unfit for use or occupation as a fortress.
Slit - a narrow opening in a wall for admitting light and for firing arrows.
Soffit - underside of arch, hung parapet, or opening.
Solar - upper living room , often over the great hall. A more private chamber for the lord of the castle and his family. Can also be sleeping quarters in general.
Spandrel - area between top of a column or pier and the apex of the arch springing from it.
Spiral Stair (Corkscrew, Turnpike) - a circular staircase - the most economical, if not the most convenient to use, method of accessing upper floors in a vertical tower; also, easier to defend.
Splay - chamfer, or sloping face.
Splayed opening - a window or door opening with angled sides in the thickness of a wall that allow more light to enter than is possible with straight sides.
Spring - level at which the springers (voussoirs) of an arch rise from their supports.
Springer - point from which an arch or vault is struck from a wall face.
Spur - a triangular buttress used to strengthen the bottom of a round tower (giving it a square base).
Squinch arch - arched support for an angle turret that does not reach the ground.
Squint - Observation hole in wall or room.
Squire - young man who served a knight, helping him with his horses and armour, who hoped to become a knight himself.
Steward - official in charge of running a lord's estate; managing work, keeping accounts, etc.
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.
Stronghouse - a mansion capable of being defended.

Tau cross - plain T cross with equal limbs.
Tenaille - low earth or masonry structure, built in the ditch to protect the curtain.
Terreplein - surface of rampart behind the parapet where guns are mounted.
Tower - defensive towers were placed at strategic places along the curtain wall (corners, changes of direction, mid-wall) to provide flanking protection; at first mostly square, they were built round as time went on with a resulting better field of fire. The D-shaped tower was even superior, with a defensive round side facing the field, and a square side (which allowed for more convenient rectangular rooms) facing the Ward.
Tower-house - form of small castle, common in Scotland, consisting mainly or entirely of a single tower
Tooth-in - stones removed (or omitted) to allow another wall to be bonded into it.
Trace - circuit or fortified perimeter, also known as the enceinte.
Tracery - intersecting ribwork in upper part of window.
Transom - horizontal division of window; crossbar.
Traverse - small bank or wall that cuts across the line of a covered way.
Trebuchet or Ballista - siege engine in the form of a large catapult.
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.
Turnpike- a circular staircase - the most economical, if not the most convenient to use, method of accessing upper floors in a vertical tower; also, easier to defend.
Turret - small tower, round or polygonal; usually a lookout.
Tympanum - space between lintel and arch over doorway.

Vault - a stone arched ceiling. (A Barrel Vault was round rather than pointed in the Gothic style.)
Vice - spiral stair.
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 - also known as mural stair. Staircase built into the thickness of a wall.
Wall-walk - passage along the top of a castle wall; may be roofed.
Ward - a castle courtyard or bailey.
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.

Yett - iron lattice gate. Similar to portcullis.