Five Classical orders, three Greek and two Roman, comprise the types of columns we use even in today's architecture. In Western-based architecture, anything called "classical" means it's from the civilizations of ancient Greece and Rome.

Each style has distinctive capitals at the top of columns and horizontal entablatures which it supports, while the rest of the building does not in itself vary between the orders. The column shaft and base also varies with the order, and is sometimes articulated with vertical hollow grooves known as fluting.

The design of most classical columns incorporates entasis (the inclusion of a slight outward curve in the sides) plus a reduction in diameter along the height of the column, so that the top is as little as 83% of the bottom diameter.