Parts of a church, working east to west:

APSE
Semi-circular recess, usually found at the east end of nave; can also be found at east end of aisles and on east side of transepts

CONCH ("conk")
Vault of an apse. Semi-dome.

AMBULATORY
Walkway, usually taken to be the walkway around the east end of the church.

SANCTUARY/PRESBYTERY
Both mean the area immediately surrounding the main altar (note spelling of altar!)

CHOIR/CHANCEL
Both mean the area between the apse or sanctuary and the crossing.

CHEVET
Choir surrounded by ring of linked chapels, especially when those chapels are kind of fused together.

CROSSING
Open area where the nave and transepts meet

TRANSEPT
Passage running north-south of nave and aisles. Some churches have several transepts.

NAVE
Main passage running west-east, leading to crossing.

AISLE
Minor passage flanking the nave. Some churches have multiple aisles.

NAVE ARCADE
Row of arches on piers on each side of the nave.

PIER
Vertical support member of any shape.

GALLERY
Vaulted passageway above the aisles, as wide as the aisles. Its vault leans against the base of the vault of the nave; it has windows in its outside wall and arched openings into the nave.

TRIFORIUM
Wall passage just under the clearstory. It has arched openings into the nave, and can have windows in its outside wall.

CLEARSTORY/CLERESTORY
Wall area with windows at the top of the nave.

WESTWERK
Pre-Gothic twin-towered façade with large Imperial audience window above central portal. Contains narthex, with Imperial viewing gallery or chapel above. It is the origin of the Gothic twin-towered façade.

PORTAL
Important doorway

NARTHEX
Hall-like area behind the façade, screened from the nave.

PORCH
Hall-like area in front of the façade.

FAÇADE
Exterior elevation, usually of front of building.

Vaulting Terms

VAULT
Curved stone roof (not a ceiling). All surfaces are curved. All surfaces are self supporting. All ribs and bosses attached to vault are decorative only.

BARREL VAULT
Continuous vault, semi-circular in section

POINTED BARREL VAULT
Continuous vault, pointed in section.

TRANSVERSE ARCH
Decorative arch that runs accross a barrel vault or pointed barrel vault. Usually seen in series.

GROIN VAULT
The crossing of two barrel vaults. Arris irregular in shape.

ARRIS
The continuous peak where two barrel vaults meet.

DOMED-UP GROIN VAULT
Groin vault organized around semi-circular diagonal arrises (contrast plain groin vault, above).

POINTED-UP GROIN VAULT
Groin vault organized around pointed diagonal arrises (contrast domed-up groin vault, above). Found at Cluny III and in its copies. (NB: Use for my courses only! I have invented this term to emphasise the structure and shape of the vault).

RIB VAULT
Domed-up groin vault (or pointed-up groin vault) whose structure is emphasised with decorative ribs.

BOSS
Decorative carving where the ribs of a vault meet.