Architectural and Engineering Glossary


Approved Ground

A ground (such as the steel framework of a building,a concrete-encased electrode,or a ground ring) that meets the requirements of the National Electrical Code or other applicable code.

Approving Authority

The individual agency,board,department,or official established and authorized by a political subdivision (e.g.,state,province,county,city,or parish) which is created by law to administer and enforce specified requirements.


On drawings,abbr.for “approximate.”


1.Any built-in,nonstructural portion of a building,such as doors,windows,ventilators,electrical equipment,partitions,etc.2.An incidental property right,as a right- of-way.appurtenance 1.Any built-in,nonstructural portion of a building,such as doors,windows,ventilators, electrical equipment,partitions,etc.2.An incidental property right,as a right of way.

Appurtenant Structure

A structure attached to the exterior of a building or erected on the roof, usually designed to support service equipment or to support a billboard or the like.

Apron Flashing

1.The flashing that covers the joint between a vertical surface and a sloping roof,as at the lower edge of a chimney.2.The flashing that diverts water from a vertical surface into a gutter.

Apron Lift

A hydraulic or mechanical lift which extends the fixed apron of a stage in front of a proscenium opening.

Apron Lining

The piece of boarding which covers the rough apron piece of a staircase.

Apron Rail

A lock rail having a raised ornamental molding.

Apron Sink

A deep-sided sink whose front and sides are extended downward from the upper edge,forming an apron around the sink.

Apron Stage

In a proscenium theater,an extension of the fixed apron (in front of a proscenium opening) by means of a platform or by an apron lift.

Apron Wall

In an exterior wall,a panel which extends downward from a windowsill to the top of a window below.


A semicircular (or nearly semicircular) or semipolygonal space,usually in a church,terminating an axis and intended to house an altar.

Apse Aisle

An aisle or ambulatory extending around an apse or chevet.

Apse Chapel

A chapel opening from an apse;such a radial chapel is a conspicuous feature of French Gothic architecture.


Pertaining to an apse or similar to one.


A small apsidal chapel, projecting from an apse.There are often several chapels projecting from the apse.


The semicircular termination of any rectangular chamber;an apse.


Descriptive of a classical temple or similar building that has no columns along the sides but may have a portico at one or both ends.


On drawings,abbr.for “architectural projected window.”


A channel for supplying water;often underground,but treated architecturally on high arches when crossing valleys or low ground.


A water-bearing formation of gravel,permeable rock,or sand that is capable of providing water,in usable quantities,to springs or wells.


A tympanum decorated with carvings.


1.On drawings,abbr.for “as required.”2.On drawings,abbr.for “as rolled.”


Any Classical structure elevated above the general ground level which is used to make offerings to the gods.


1.Intricate overall pattern of geometric forms or stylized plants used in Muslim countries.2.Overall decorative pattern of acanthus scrolls,swags,candelabrum shafts,animal or human forms,on panels or pilasters,in Roman and Renaissance architecture.3.A species of ornament of infinite variety used for enriching flat surfaces or moldings,either painted,inlaid,or carved in low relief.

Arabic Arch

A horseshoe arch.

Arc Cutting

A process of cutting or removing metal by melting it with the heat produced between an electrode and the metal being cut.

Arc Light

A high intensity light source produced by an arc,usually,between two metal electrodes or between two carbon rods;also see carbon arc spotlight.

Arc Spotlight

See carbon arc spotlight.

Arc Weld

A weld in which the heat of fusion is supplied by an electric arc.

Arc Welding

The joining of metal parts by fusion,in which the necessary heat is produced by means of an electric arc,sometimes accompanied by the use of a filler metal and/or the application of pressure.


Same as flying buttress.


In ancient Roman architecture,the gutters of the cavaedium.

Arch Band

Any narrow elongated surface forming part of,or connected with,an arch.

Arch Bar

A curved wrought iron or steel bar used to support the weight of the masonry above a fireplace or window opening.

Arch Barrel Roof

See barrel vault.

Arch Beam

Same as arched beam.

Arch Brace

A curved brace,usually used in pairs to support a roof frame and give the effect of an arch.

Arch Buttant

Same as flying buttress.

Arch Buttress

Same as flying buttress.

Arch Center

Formwork to support the voussoirs of an arch during construction.

Arch Corner Bead

A corner bead that is cut on the job;used to form and reinforce the curved portion of an arch opening.

Arch Order

1.In Roman architecture,arches enframed by engaged columns and entablatures.2.In medieval architecture,successive vertical planes of arches and colonettes set one within another.

Arch Rib

1.In Romanesque architecture,a transverse rib crossing the nave or aisle at right angles to its length.2.A principal load-bearing member of a ribbed arch.

Arch Ring

In an arched structure,the curved member that sustains the principal load.

Arch Stone

Same as voussoir.

Arch Surround

A seldom used term for a decorative border around an arch;same as archivolt. 

Arch Truss

 A truss having an arched upper chord (concave downward) and a straight bottom chord;there are vertical hangers between the two chords. 


On drawings,abbr. for architect,architecture,or architectural.