Arrow Loop – A narrow vertical slit cut into a wall through which arrows could be fired.
Bailey – Courtyard.
Ballista – Engine resembling a crossbow, used in hurling missiles or large arrows.
Baluster – A short shaft, such as is used in balustrades, usually thicker in the middle than at the ends.
Barbican – An outwork or forward extension of a castle gateway.
Bastille – Redoubt or outwork.
Bastion – A small tower at the end of a curtain wall or in the middle of the outside wall.
Batter – A sloping part of a curtain wall. The sharp angle at the base of all walls and towers along their exterior surface.
Battlement – Narrow wall built along the outer edge of the wall walk
Bay – A constituent portion or compartment of a building, complete in itself and corresponding to other portions.
Berm – Flat space between the base of the curtain wall and the inner edge of the moat.
Buttery – Room for the service of beverages.
Cat – Assault tower.
Catapult – Stone-throwing engine, usually employing torsion.
Cesspit – The opening in a wall in which the waste from one or more garderobes was collected.
Chamfer – A surface formed by paring off an angle.
Chemise – Inner walled enclosure of a castle.
Corbel – A stone or timber bracket supporting a projection from a wall.
Crenelation – A notched battlement made up of alternate crenels (openings) and merlons (square saw-teeth).
Curtain – Those portions of a fortified wall which connect adjacent flanking-towers.
Daub – A mud of clay mixture applied over wattle to strengthen and seal it.
Dead angle – An angle, the ground contained by which cannot be seen by the defenders, and is therefore indefensible.
Dongjon or keep – The inner stronghold of a castle, usually found in one of the towers.
Drawbridge – A heavy timber platform built to span a moat between a gate house and surrounding land that could be raised when required to block an entrance.
Embrasure – The low segment of the alternating high and low segments of a battlement.
Enceinte – An enclosing wall, usually exterior, of a fortified place.
Escalade – Scaling of a castle wall.
Finial – A slender piece of stone used to decorate the tops of the merlons.
Forebuilding – A projection in front of a keep or donjon, containing the stairs to the main entrance.
Garderobe – Small latrine or toilet, either built into the thickness of the wall or projected out from it.
Gate House – The complex of towers, bridges, and barriers built to protect each entrance through a castle or town wall.
Great Hall – the building in the inner ward that housed the main meeting and dining area for the castle’s residents.
Groining – The angular edges formed by the intersection of vaults in a ceiling.
Half-timber – The common form of medieval construction in which walls were made of a wooden frame structure filled with wattle and daub.
Hall – Principal living quarters of a medieval castle or house.
Hall for hynds – Servants’ hall.
Herring-bone pattern – The placing of stones aslant in a wall so that each two rows form a succession of angles resembling the backbone of a herring.
Hoarding – A temporary wooden balcony suspended from the tops of walls and towers before a battle, from which missiles and arrows could be dropped or fired accurately toward the base of the wall.
Inner Curtain – The high wall that surrounds the inner ward.
Inner Ward – The open area in the center of a castle.
Keep – See donjon.
Lantern or louvre – A small open turret placed on a roof as an outlet for smoke.
Lights – The spaces between the mullions of a window.
Machicolation – A projection in the battlements of a wall with openings through which missiles can be dropped on besiegers.
Mangonel – A form of catapult.
Merlon – The high part of the square “sawtooth” between crenels in a battlement.
Meurtriere – Arrow loop, slit in battlement or wall to permit firing of arrows, or for observation.
Moat – A deep trench dug around a castle to prevent access from the surrounding land. It could be either left dry or filled with water.
Motte – An earthwork mound on which a castle was built.
Mullions – The vertical divisions of stone or wood between the lights of windows.
Oriel – Projecting room on an upper floor.
Outer Curtain – The wall which enclosed 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 could be erected.
Parapet – Protective wall at the top of a fortification, around the outer side of the wall-walk.
Pier – The mass of masonry between arches and other openings.
Pilaster – A square or rectangular pillar, engaged in, and projecting slightly from, a wall.
Portcullis – Vertical sliding wooden grille shod with iron suspended in front of a gateway, let down to protect the gate.
Postern or sally-port – Secondary gate or door.
Putlog Hole – A hole intentionally left in the surface of a wall for insertion of a horizontal pole.
Quoins – Dressed corner-stones.
Ram – Battering-ram.
Rubble – A random mixture of rocks and mortar.
Sapping – Undermining, as of a castle wall.
Scaffolding – The temporary wooden framework built next to a wall to support both workers and materials.
Screens – Wooden partition at the kitchen end of a hall, protecting a passage leading to the buttery, pantry, and kitchen.
Solar – Originally a room above ground level, but commonly applied to the great chamber or a private sitting room off the great hall.
Springald – War engine of the catapult type, employing tension.
Steward – The man responsible for running the day-to-day affairs of the castle in the absence of the lord.
Trebuchet – War engine developed in the Middle Ages employing counterpoise.
Truss – One of the timber frames built to support the roof over the Great Hall.
Turret – A small tower rising above and resting on one of the main towers, usually used as a lookout point.
Ward – Courtyard or bailey.
Wattle – A mat of woven sticks and weeds.