Abacus <= Flat portion on top of a capital.

Aisle <= Space between arcade and outer wall.

Allure <= Walkway along the top of a wall.

Ambulatory <= Aisle round an apse.

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.).

Bonnet <= Freestanding fortification; priest's cap.

Boss <= Central stone of arch or vault; key stone.

Brattice <= 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.

Burg <= German stronghold.

Burh <= Saxon stronghold; literally a "neighborhood".

Buttery <= Next to the kitchen, a room from where wine was dispensed.

Buttress <= Wall projection for extra support; flying <= narrow, arched bridge against the structure; pilaster <= gradually recedes into the structure as it ascends.

Capital <= Distinctly treated upper end of a column.

Carotid <= Heart-shaped.

Casemates <= Artillery emplacements in separate protected rooms, rather than in a battery.

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.

Chemise wall <= Formed by a series of interlinked or overlapping semicircular bastions.

Chevron <= Zig-zag moulding.

Choir <= The part of a cruciform church east of the crossing.

Clasping <= Encasing the angle.

Clunch <= Hard chalky material.

Cob <= Unburned clay mixed with straw.

Column <= Pillar (circular section).

Concentric <= Having two sets of walls, one inside the other.

Coping <= Covering stones.

Corbel <= A projecting block of stone built into a wall during construction; step-wise construction, as in an arch, roof, etc.

Corinthian <= Elaborately foliated capital.

Cornice <= Decorative projection along the top of a wall.

Counterguard <= A long, near-triangular freestanding fortification within the moat.

Counterscarp <= Outer slope of ditch.

Course <= Level layer of stones or bricks.

Crannog <= Celtic Scotland timber-built fortified lake village.

Creasing <= þ-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 <= Battlements at the top of a tower or wall.

Crocket <= Curling leaf-shape.

Cross-and-orb <= Modified cross slits to accommodate gunnery.

Crosswall <= Interior dividing wall; structural.

Crownwork <= Freestanding bastioned fortification in front of main defenses.

Cupola <= Hemispherical armored roof.

Curtain Wall <= A connecting wall hung between two towers surrounding the bailey.

Cushion <= Capital cut from a block by rounding off the lower corners.

Cusp <= Curves meeting in a point.

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.

Diaper work <= Decoration of squares or lozenges.

Diaphragm <= Wall running up to the roof-ridge.

Dog-legged <= With right-angle bends.

Dogtooth <= Diagonal indented pyramid.

Donjon <= A great tower or keep.

Dormer <= 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.

Dressing <= Carved stonework around openings.

Drum Tower <= A large, circular, low, squat tower built into a wall.

Drystone <= Unmortared masonry.

Dungeon <= The jail, usually found in one of the towers.

Embattled <= Battlemented; crenelated.

Embrasure <= The low segment of the altering high and low segments of a battlement.

Enceinte <= The enclosure or fortified area of a castle.

Fascine <= Huge bundle of brushwood for revetting ramparts or filling in ditches.

Fillet <= Narrow flat band.

Finial <= A slender piece of stone used to decorate the tops of the merlons, spire, tower, balustrade, etc.

Fluting <= Concave mouldings in parallel.

Foliated <= Carved with leaves.

Footings <= Bottom part of wall.

Forebuilding <= An extension to the keep, guarding it's entrance.

Fosse <= Ditch.

Freestone <= High quality sand- or lime-stone.

Fresco <= Painting on wet plaster wall.

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.

Gate House <= The complex of towers, bridges, and barriers built to protect each entrance through a castle or town wall.

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.

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.

Groined <= Roof with sharp edges at intersection of cross-vaults.

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 complex.

Herringbone <= Brick or stone laid in alternate diagonal courses.

Hillfort <= Bronze or iron age earthwork defenses of concentric ditches and banks.

Hoarding <= 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.

Hood <= Arched covering; when used as umbrella, called hood-mould.

Hornwork -Freestanding quadrilateral fortification in front of the main wall.

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.

Jamb <= Side posts of arch, door, or window.

Joggled <= Keyed together by overlapping joints.

Joist <= Wall-to-wall timber beams to support floor boards.

Keep <= A strong stone tower; main tower; donjon; stronghold.

Keystone <= Central wedge in top of arch.

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.

Loophole <= Narrow, tall opening, wallslit for light, air, or shooting through.

Louvre <= Opening in roof (sometimes topped with lantern) to allow smoke to escape from central hearth.

Lozenge <= Diamond shape.

Machicolations <= Projecting gallery on brackets, on outside of castle or towers, with holes in floor for dropping rocks, shooting, etc.

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.

Meurtriere <= An opening in the roof of a passage where soldiers could shoot into the room below. Also see "Murder Holes".

Moat <= A deep trench usually filled with water that surrounded a castle.

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 <= Earth mound 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.

Mural <= Wall (adjectival).

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

O”lite <= 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.