A column in in architecture is a vertical support consisting of a base, an approximately cylindrical shaft, and a capital. The term "column" is loosely used in a general sense for any isolated support, such as a post (a slender support without capital or base) or a pier, which may have a rectangular shaft or a cluster of small shafts and may lack a capital.
The earliest columns were simply tree trunks. Later, in ancient civilizations columns came to be made of stone. In modem times columns are sometimes wooden copies of stone columns. The shaft of a column is usually composed of drums or cylinders superimposed on one another, although it may be in one solid piece. The unit of measurement of the height of a column is the diameter of the shaft at the base; thus, a column may be said to be 10 lower diameters high.
The chief purpose of a column is to support a roof beam, entablature, or arch. Most columns are free-standing; some, however, are engaged, that is, part of the circumference is embedded in a wall. Occasionally a column may stand alone as a monument, perhaps with a statue on its capital. Examples of monumental columns are the commemorative columns of Trajan and Marcus Aurelius in Rome and The Monument in London, recalling the great fire that swept the city in 1666.
Most ancient Egyptian columns are often derived from plant forms. A common style has a shaft grooved to look like a bundle of stems of the lotus or papyrus plants. The shaft broadens slightly just above a disklike base, as do the stems of these plants above their roots. The shaft then narows slightly toward the top, ending just below the capital in horizontal moldings that look like cords binding several stems together. (The columns of the side aisles of the Temple of Amon-Ra at Karnak keep the outline of the stem cluster but have abandoned the suggestion of individual stems in favor of a cylindrical shaft.) Some Egyptian capitals are shaped like a bud, bulging out above the cord and then tapering to hold a square stone block supporting the roof beam. Other capitals, suggesting a bell-shaped, open lotus, flare out to hold the block. Leaves are painted on the base of the shaft, and sepals and petals adorn the capital.
Classical Greece developed three types of columns - Doric, Ionic, and Corinthian - that have influenced architecture ever since. A Doric column has no individual base; it rests on the stylobate (top step of the temple), which serves as a collective base for the shafts of all the columns. A Doric column is relatively short, only four diameters high in early temples, about five and a half diameters high in the Parthenon of the 5th century B.C. The Shaft tapers in a flat curve, called entasis, but is never wider than at the bottom. The height of the shaft is accented by fluting (vertical grooves). In Doric columns the flutes are relatively shallow and meet in an arris (ridge), and their number varies from temple to temple. (The columns of the Parthenon have 20 flutes.) The Doric capital consists of a necking, in which the flutes terminate, a cushion-like echinus that bulges beyond the top of the shaft, and an abacus, a square block to support the entablature.
The Ionic column has a base that is usually composed of a torus (convex-molding), a scotia (concave molding), and another torus. There are variations. The Ionic shaft is taller and more slender than the Doric, with 24 semicircular flutes separated by fillets (narrow bands). The Ionic capital is distinguished by two pairs of scrolls, on the front and the back, each joined by a graceful curve under a very thin abacus. As a result, the front view of the capital differs from the side view. Therefore, in order to give the capital at the corner of a temple a unified appearance with the capitals extending in either direction from the comer, Greek architects bent the corner scroll outward to an angle of 45 degrees.
The Corinthian column has a base and shaft similar to the Ionic. Its capital, however, is bell-shaped with two staggered rows of acanthus leaves and four small diagonal scrolls under the corners of the abacus.
Roman and Later
Rome inherited the Greek forms of columns and added to them the Tuscan, a plainer version of the Doric, and the Composite, whose capital combines Ionic scrolls and Corinthian leafage. The Romans also modified some other details of the older forms. For example they provided separate molded bases for the Doric column and converted the free-hand curve of its echinus into a quarter-round molding. Sometimes fluting was omitted, especially on columns made of colored marbles. According to the canon of mathematical proportions prescribed by the Roman architect Vitruvius in the 1st century B.C., the Tuscan column should be seven lower diameters in height, the Doric eight, the Ionic nine, and the Corinthian and Composite ten.
During the Middle Ages the classical orders were modified and mixed, with Byzantine, Moorish, and regional influences leading to a great variety of styles in columns. In the Renaissance such architectural theorists as Alberti, Palladio, and Vignola revived the classical orders of columns which persisted into the baroque period and the late 18th century. These forms continued to be used in the 19th and 20th centuries, especially for public buildings. See also capital; greek architecture.