Referring to the columns and entablature as a system. Description: The column was, moreover, constructed in three principal styles or orders, each possessing characteristic forms and proportions of its own, distinctive of the order, but by unprofessional persons most readily distinguished by the difference in the capitals. Doric; the oldest, most substantial, and heaviest of all, which has no base, and a very simple capital. Ionic; the next in lightness, which is furnished with a base and has its capital decorated with volutes. Corinthian; the lightest of all, which has a base and a plinth below it, and a deep capital ornamented with foliage. To these are often added: Tuscan; only known from the account of Vitruvius, and which nearly resembled the Roman Doric; and Composite; a mixed order, formed by combining the volutes of the Ionic with the foliage of the Corinthian. Generally columns are used in a row (a colonnade) to carry an entablature, but they were also used singly for decorative or commemorative purposes. Engaged columns are columns which are attached to the wall rather than free standing; they may be half-columns or three-quarter columns.