Glossary
- Oratory
- A private chapel in a church or house. Also a church of the Oratorians (Roman Catholic).
- Order
- One of a series of recessed arches and jambs forming a splayed medieval opening, e.g. a doorway or arcade arch. Also, an upright structural member used in series, especially in classical architecture: see Orders.
- Orders
- The differently formalized versions of the basic post-and-lintel (column and entablature) system in classical architecture. The main orders are Doric, Ionic, and Corinthian. They are Greek in origin but occur in Roman versions. Tuscan is a simple variant of Roman Doric. The Composite capital combines Ionic volutes with Corinthian foliage. Though each order has its own conventions of design and proportion, there are many minor variations. Superimposed orders: orders on successive levels, customarily in the upward sequence of Tuscan, Doric, Ionic, Corinthian, Composite.
- Organ loft
- In a church, a gallery in which the organ is placed.
- Oriel
- A bay window which rests on corbels or brackets and starts above ground level.
- Overarch
- An arch framing an opening in a wall, e.g. a window or door.
- Overdoor
- Painting or relief above an internal door. Also called a sopraporta.
- Overmantel
- An ornamented or painted feature above a fireplace.
- Overshot water wheel
- One with water fed on to the wheel over the top. Compare breastshot, pitchback and undershot.
- Overthrow
- Decorative fixed arch between two gatepiers or above a gate, often of iron.
