Editing Arch (section)

=== Terminology ===
{{Redirect|False arch|an arch-like construction that uses offsetting of the stones or bricks, "corbelling", to close the span|Corbel arch}}
A '''true arch''' is a load-bearing arch with elements held together by compression.{{sfn | Woodman | Bloom | 2003 | loc=}} In much of the world introduction of the true arch was a result of European influence.{{sfn | Woodman | Bloom | 2003 | loc=History }} The term '''false arch''' has few meanings. It is usually used to designate an arch that has no structural purpose, like a [[proscenium arch]] in theaters used to frame the performance for the spectators, but is also applied to [[Corbel arch|corbelled]] and [[Triangular arch|triangular]] arches that are not based on compression.{{sfn | Woodman | Bloom | 2003 | loc=False}}{{sfn | Woodman | Bloom | 2003 | loc=Triangular}}

[[File:Arch illustration.svg|thumb|upright=1|Masonry arch elements]]
A typical true [[masonry]] arch consists of the following elements:{{sfn|Boyd|1978|p=90}}{{sfn | Wilkins | 1879 | pp=291-293}}{{sfn | Woodman | Bloom | 2003 | loc=Structure}}
# [[Keystone (architecture)|Keystone]], the top block in an arch. Portion of the arch around the keystone (including the keystone itself), with no precisely defined boundary, is called a '''crown'''  
# [[Voussoir]] (a wedge-like construction block). A [[compound arch]] is formed by multiple concentric layers of voussoirs. The '''rowlock arch''' is a particular case of the compound arch,<ref>{{M-W|rowlock arch}}</ref> where the voussoir faces are formed by the [[brick header]]s.{{sfn|American Technical Society|1908|p=111}} 
# '''Extrados''' (an external surface of the arch) 
# [[Impost (architecture)|Impost]] is block at the base of the arch (the voussoir immediately above the impost is a [[springer (architecture)|springer]]). The tops of imposts define the '''springing level'''. A portion of the arch between the springing level and the crown (centered around the 45° angle{{sfn | Woodman | Bloom | 2003 | loc=Haunch}}) is called a '''haunch'''. If the arch resides on top of a [[column]], the impost is formed by an [[Abacus (architecture)|abacus]] or its thicker version, [[dosseret]].{{sfn | Woodman | Bloom | 2003 | loc=Dosseret}}
# '''Intrados''' (an underside of the arch, also known as a ''[[soffit]]''{{sfn | Woodman | Bloom | 2003 | p=}}) 
# '''Rise''' (height of the arc, distance from the springing level to the crown)
# [[Clear span]]
# [[Abutment]]{{sfn | Beall | 1987 | p=301}} The roughly triangular-shaped portion of the wall between the extrados and the [[Division (architecture)|horizontal division]] above is called ''[[spandrel]]''.{{sfn | Woodman | Bloom | 2003 | loc=Intrados}}

A (left or right) half-segment of an arch is called an ''arc'', the overall line of an arch is ''arcature''{{sfn | Woodman | Bloom | 2003 | loc=Arc}} (this term is also used for an [[Arcade (architecture)|arcade]]).<ref>{{M-W|arcature}}</ref> [[Archivolt]] is the exposed (front-facing) part of the arch, sometimes decorated (occasionally also used to designate the intrados).{{sfn | Woodman | Bloom | 2003 | loc=Archivolt}} If the sides of voussoir blocks are not straight, but include angles and curves for interlocking, the arch is called "[[Joggle (architecture)|joggled]]".{{sfn | Woodman | Bloom | 2003 | loc=Joggled}}