How did the Doric order differ from the Ionic order in ancient Greek architecture?

In Western architecture, the Doric order and Ionic order are distinguished by several key structural and aesthetic differences.1

Column and Base

• Doric: These columns are the most squat, typically measuring four to eight lower diameters in height. Greek Doric columns traditionally lack an individual base, resting directly on the stylobate. The shaft features 20 shallow flutes.1
• Ionic: These are more slender, with the entire order measuring nine lower diameters in height. The column base consists of two convex moldings (tori) separated by a concave scotia, and the shaft contains 24 flutes.1

Capital

• Doric: The capital is simple, consisting of a necking, a spreading convex echinus, and a square abacus.1
• Ionic: The capital is defined by volutes—scrolls that droop over the front and rear of the echinus—which is often carved with an egg-and-dart motif.1

Entablature

• Doric: The frieze is characterized by alternating triglyphs and metopes.1
• Ionic: The architrave is typically composed of three stepped bands, and the frieze lacks triglyphs, allowing for a continuous band of carved ornament.1