Arrow Loops - Narrow slits in a curtain wall or tower from which to fire arrows. Usually cross shaped to allow more range horizontally.
Bailey - Walled enclosure or courtyard of a castle; ward.
Ballista - Castle siege engine shaped like a large crossbow, for shooting large arrows.
Barbican - Outer defensive work, usually located in front of a castles gate.
Barrel Vault - Semicircular roof of stone or timber.
Bastion - Gun platform projecting from an angle of the walls of a castle to expose attackers on either side to fire.
Battering Ram - Large beam of wood capped with a metal tip. Used to knock down castle gates.
Belfry (Or Siege Tower) - Tower built of wood which was wheeled up to the castle walls so attackers could storm the castle from the top of the belfry via a wooden bridge onto the castle parapet.
Bergfried - Type of German castle with a slender tower.
Berm - Flat area between a rampart or wall and its associated ditch.
Bombard - Early form of cannon.
Buttress - Vertical stone reinforcing strip for a wall.
Corbel - Stone bracket.
Counter-Castle(Or Siege-castle) - Temporary structure built close to a besieged castle in order to blockade the castle or provide protection for attackers.
Crenel - Open section of a battlement.
Crenellation - Arrangement of battlements into a line of alternating merlons and crenels.
Curtain Wall - Outer wall of a fortification linking towers and gates to form an enclosure.
Donjon - Great tower or keep.
Drawbridge - Lifting bridge that could be raised to keep out an enemy.
Dressing - Carved or smoothed stonework around openings and along edges.
Drum-Tower - Large, circular tower, usually shorter and wider then a normal tower.
Embrasure - Open area set inside the thickness of a wall behind a loophole or arrowslit for archers to stand in.
Escalade - Attempting to storm a castle by scaling the walls with ladders.
Gallery - Long narrow passage or room.
Ganerbenburg - Castle in which several families shared common areas of the castle including the courtyard, well and chapel while also maintaining their own private living quarters.
Garderobe - Latrine, usually set over a stone shaft or drain.
Hoarding - Covered wooden gallery affixed to the top of the outside of a tower or curtain wall to defend a castle.
Machicolation - Battlement brought forward on corbels to allow material to be dropped through gaps.
Mangonel - Catapult, sometimes referred to as a traction trebuchet or a torsion engine.
Mantlet - Mobile wooden protective shield on wheels.
Merlon - Solid section of a battlement.
Moat - Ditch surrounding a castle, either filled with water or dry.
Motte - Earthwork mound topped with a tower or shell keep.
Murder Holes (Meurtriere) - Holes cut through the ceiling of a gatehouse used to drop fire or burning oil from above onto anyone trying to attack the castle gate. Also used to drop water on to a gate that was set on fire by the enemy.
Newel - Center support column of a spiral staircase.
Oriel Window - Projecting curved or polygonal window.
Oubliette - Dungeon or pit under the floor, reached by a trap door, used for incarcerating prisoners. French transliation: place to be forgotten.
Palisade - Strong wooden fence.
Parapet - Low wall on top of and outside the main wall, which protected the wall-walk. Most Parapets had merlons and crenels along the tops to form crenallations which allowed archers to shoot arrows while still being protected behind the castle walls.
Pele Tower (also called a Peel Tower) - Small fortified keeps or tower houses built along the English and Scottish borders intended as watch towers where signal fires could be lit by the garrison to warn of approaching danger.
Petrary - Stone throwing engine.
Portcullis - Heavy iron tipped wooden grill or gate that is raised and lowered vertically inside a castles gatehouse or entryway.
Postern - Lesser or private gate.
Quatrefoil - Four-lobed.
Quoin - Dressed cornerstone at an angle of a building.
Rampart - wall or bank of excavated earth surrounding a castle which was used to defend against attacks, usually topped with a palisade or stone wall.
Rayere - Tall narrow opening for admitting light in a thick castle wall.
Ringwork - Earthwork castle which has no identifiable strongpoint or motte.
Rubble - Uncut or roughly shaped stone, for walling.
Sally-Port - Side gate for defenders to go out on an attack.
Shell-Keep - Motte in which the palisade around the top is replaced by a stone wall without a tower.
Siege-Castle - See Counter castle.
Siege Tower - See Belfry.
Slight - To damage or destroy a castle to render it unfit for use or occupation as a fortress.
Solar - Lord's parlour or private quarters.
Tenshu - Large main tower of a Japanese castle.
Tower House - Form of a small castle consisting of a single tower, common in Scotland.
Trebuchet - Extremely powerful siege engine that worked by counter balancing weights or stones to generate propulsion for a swinging wooden arm used to launch giant stones at castle walls.
Turning Bridge - Counterbalanced bridge in which weights on the inner end allow the outer end to swing up quickly.
Wall-Walk - Path along the top of a wall, protected by a parapet.
Wing-Wall - Wall descending the slope of a motte.