The various orders are recognized and distinguished mainly by the shape of the column "Column (architecture)"), and more specifically by that of its capital. The Greeks only used three orders: Doric, Ionic and Corinthian. The Romans assumed the Greek orders and transformed them, creating their own version, while adding two more: Tuscan and Composite. Although they have the same name, the three Greek orders are different from the Roman ones, especially the Doric style.[2]​.

The most representative construction element is the column. It is divided into three parts: base, shaft and capital. In the Greek Doric order, the column has no base. In classical buildings, the columns support the horizontal structure called the entablature, which is normally made up of three overlapping parts: architrave, frieze and cornice. Sometimes the complex is erected on a podium "Podium (architecture)") or pedestal: the stylobate.[2]​.

The design of classical buildings is rigorously modular, maintaining strict proportions based on a unit of measurement, or "module", specific to each one of them, which corresponds to the radius of the shaft at its base. In this way, if it is said that a column has a height of twelve modules, it means that it is equal to twelve times the lower radius of the shaft.[2]​.

In each order, each part of the building invariably has a fixed and predetermined number of modules. In the 19th century, the Italian Jacopo Vignola studied and systematized the classical orders, establishing their modular canons and defining in detail their measurements and geometric layout systems for the use of his contemporaries. All this was included in his treatise Regola delli cinque ordini d'architettura.[2]​.

The Tuscan and Doric orders are the simplest and were used outdoors, especially in temples dedicated to male gods. The Ionic, Corinthian and Composite styles were used both inside and outside the temples dedicated to female deities.[2]​.

When several orders overlapped, they were organized from simplest to most complex, always placing the simplest ones in the lower areas of the building.[2]​.

The various orders are recognized and distinguished mainly by the shape of the column "Column (architecture)"), and more specifically by that of its capital. The Greeks only used three orders: Doric, Ionic and Corinthian. The Romans assumed the Greek orders and transformed them, creating their own version, while adding two more: Tuscan and Composite. Although they have the same name, the three Greek orders are different from the Roman ones, especially the Doric style.[2]​.

The most representative construction element is the column. It is divided into three parts: base, shaft and capital. In the Greek Doric order, the column has no base. In classical buildings, the columns support the horizontal structure called the entablature, which is normally made up of three overlapping parts: architrave, frieze and cornice. Sometimes the complex is erected on a podium "Podium (architecture)") or pedestal: the stylobate.[2]​.

The design of classical buildings is rigorously modular, maintaining strict proportions based on a unit of measurement, or "module", specific to each one of them, which corresponds to the radius of the shaft at its base. In this way, if it is said that a column has a height of twelve modules, it means that it is equal to twelve times the lower radius of the shaft.[2]​.

In each order, each part of the building invariably has a fixed and predetermined number of modules. In the 19th century, the Italian Jacopo Vignola studied and systematized the classical orders, establishing their modular canons and defining in detail their measurements and geometric layout systems for the use of his contemporaries. All this was included in his treatise Regola delli cinque ordini d'architettura.[2]​.

The Tuscan and Doric orders are the simplest and were used outdoors, especially in temples dedicated to male gods. The Ionic, Corinthian and Composite styles were used both inside and outside the temples dedicated to female deities.[2]​.

When several orders overlapped, they were organized from simplest to most complex, always placing the simplest ones in the lower areas of the building.[2]​.