arch: A curved structural member spanning an opening or recess. The wedge shaped elements that make up an arch keep one another in palce and transform the vertical pressure of the structure above into lateral pressure.
Parts of an arch:
keystone,
soffit,
spring line, springer,
voussoir.
Measurements of an arch:
rise,
span.
Related architectural elements:
arcade,
cusp,
hood moulding,
spandrel,
tympanum.
See also:
intersecting arch,
blind arch,
relieving arch,
Shapes of arches.
