"An Order in architecture is a certain assemblage of parts subject to uniform established proportions, regulated by the office that each part has to perform". The Architectural Orders are the ancient styles of classical architecture, each distinguished by its proportions and characteristic profiles and details, and most readily recognizable by the type of column employed. Three ancient orders of architecture—the Doric, Ionic, and Corinthian—originated in Greece. To these the Romans added the Tuscan, which they made simpler than Doric, and the Composite, which was more ornamental than the Corinthian. The Architectural Order of a classical building is akin to the mode or key of classical music, the grammar or rhetoric of a written composition. It is established by certain modules like the intervals of music, and it raises certain expectations in an audience attuned to its language.
Each style has distinctive capitals and entablatures. The column shaft is sometimes articulated with vertical hollow grooves known as fluting. The shaft is wider at the bottom than at the top, because its entasis, beginning a third of the way up, imperceptibly makes the column slightly more slender at the top, although some Doric columns are visibly "flared", with straight profiles that narrow going up the shaft.
The capital rests on the shaft. It has a load-bearing function, which concentrates the weight of the entablature on the supportive column, but it primarily serves an aesthetic purpose. The necking is the continuation of the shaft, but is visually separated by one or many grooves. The echinus lies atop the necking. It is a circular block that bulges outwards towards the top to support the abacus, which is a square or shaped block that in turn supports the entablature. The entablature consists of three horizontal layers, all of which are visually separated from each other using moldings or bands. In Roman and post-Renaissance work, the entablature may be carried from column to column in the form of an arch that springs from the column that bears its weight, retaining its divisions and sculptural enrichment, if any.
Greek orders with full height
The height of columns are calculated in terms of a ratio between the diameter of the shaft at its base and the height of the column. A Doric column can be described as seven diameters high, an Ionic column as eight diameters high and a Corinthian column nine diameters high, although the actual ratios used vary considerably in both ancient and revived examples, but keeping to the trend of increasing slimness between the orders. Sometimes this is phrased as "lower diameters high", to establish which part of the shaft has been measured.
There are three distinct orders in Ancient Greek architecture: Doric, Ionic, and Corinthian. These three were adopted by the Romans, who modified their capitals. The Roman adoption of the Greek orders took place in the 1st century BC. The three Ancient Greek orders have since been consistently used in neo-classical European architecture.
Sometimes the Doric order is considered the earliest order, but there is no evidence to support this. Rather, the Doric and Ionic orders seem to have appeared at around the same time, the Ionic in eastern Greece and the Doric in the west and mainland.
Both the Doric and the Ionic order appear to have originated in wood. The Temple of Hera in Olympia is the oldest well-preserved temple of Doric architecture. It was built just after 600 BC. The Doric order later spread across Greece and into Sicily where it was the chief order for monumental architecture for 800 years.
The Doric order of the Parthenon
The Doric order originated on the mainland and western Greece. It is the simplest of the orders, characterized by short, faceted, heavy columns with plain, round capitals (tops) and no base. With a height that is only four to eight times its diameter, the columns are the most squat of all orders. The shaft of the Doric order is channeled with 20 flutes. The capital consists of a necking which is of a simple form. The echinus is convex and the abacus is square.
Above the capital is a square abacus connecting the capital to the entablature. The Entablature is divided into three horizontal registers, the lower part of which is either smooth or divided by horizontal lines. The upper half is distinctive for the Doric order. The frieze of the Doric entablature is divided into triglyphs and metopes. A triglyph is a unit consisting of three vertical bands which are separated by grooves. Metopes are the plain or carved reliefs between two triglyphs.
The Greek forms of the Doric order come without an individual base. They instead are placed directly on the stylobate. Later forms, however, came with the conventional base consisting of a plinth and a torus. The Roman versions of the Doric order have smaller proportions. As a result they appear lighter than the Greek orders.
The Ionic order came from eastern Greece, where its origins are entwined with the similar but little known Aeolic order. It is distinguished by slender, fluted pillars with a large base and two opposed volutes (also called scrolls) in the echinus of the capital. The echinus itself is decorated with an egg-and-dart motif. The Ionic shaft comes with four more flutes than the Doric counterpart (totalling 24). The Ionic base has two convex moldings called tori which are separated by a scotia.
The Ionic order is also marked by an entasis, a curved tapering in the column shaft. A column of the ionic order is nine times its lower diameter. The shaft itself is eight diameters high. The architrave of the entablature commonly consists of three stepped bands (fasciae). The frieze comes without the Doric triglyph and metope. The frieze sometimes comes with a continuous ornament such as carved figures instead.
The Corinthian order is the most ornate of the Greek orders, characterized by a slender fluted column having an ornate capital decorated with two rows of acanthus leaves and four scrolls. It is commonly regarded as the most elegant of the three orders. The shaft of the Corinthian order has 24 flutes. The column is commonly ten diameters high.
The Roman writer Vitruvius credited the invention of the Corinthian order to Callimachus, a Greek sculptor of the 5th century BC. The oldest known building built according to this order is the Choragic Monument of Lysicrates in Athens, constructed from 335 to 334 BC. The Corinthian order was raised to rank by the writings of Vitruvius in the 1st century BC.
The Romans adapted all the Greek orders and also developed two orders of their own, basically modifications of Greek orders. The Romans also invented the superposed order. A superposed order is when successive stories of a building have different orders. The heaviest orders were at the bottom, whilst the lightest came at the top. This means that the Doric order was the order of the ground floor, the Ionic order was used for the middle story, while the Corinthian or the Composite order was used for the top story. The Colossal order was invented by architects in the Renaissance. The Colossal order is characterized by columns that extend the height of two or more stories.
The Tuscan order in Andrea Palladio, Quattro Libri di Architettura, 1570
The Tuscan order has a very plain design, with a plain shaft, and a simple capital, base, and frieze. It is a simplified adaptation of the Doric order by the Romans. The Tuscan order is characterized by an unfluted shaft and a capital that only consists of an echinus and an abacus. In proportions it is similar to the Doric order, but overall it is significantly plainer. The column is normally seven diameters high. Compared to the other orders, the Tuscan order looks the most solid.
The Composite order is a mixed order, combining the volutes of the Ionic with the leaves of the Corinthian order. Until the Renaissance it was not ranked as a separate order. Instead it was considered as a late Roman form of the Corinthian order. The column of the Composite order is ten diameters high.