In architecture the capital or chapiter forms the topmost member of a column. It mediates between the column and the load thrusting down upon it, broadening the area of the column's supporting surface. The capital, projecting on each side as it rises to support the abacus, joins the usually square abacus and the usually circular shaft of the column. The capital may be convex, as in the Doric order; concave, as in the inverted bell of the Corinthian order; or scrolling out, as in the Ionic order. These form the three principal types on which all capitals in the classical tradition are based. The Composite order established in the 16th century on a hint from the Arch of Titus, adds Ionic volutes to Corinthian acanthus leaves.
Illustration of papyriform capitals, in The Grammar of Ornament, 1856
Nine types of capitals, from The Grammar of Ornament
Columns with Hathoric capitals, at the Temple of Isis from island Philae
Egyptian composite columns from Philae
A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. The term column applies especially to a large round support with a capital and a base or pedestal, which is made of stone, or appearing to be so. A small wooden or metal support is typically called a post. Supports with a rectangular or other non-round section are usually called piers.
National Capitol Columns at the United States National Arboretum in Washington, D.C.
Columns of the Parliament House in Helsinki, Finland
Column of the Gordon Monument in Waterloo.
Dragon pillar from the Yingzao Fashi, Song dynasty