<P> The Ionic order forms one of the three classical orders of classical architecture , the other two canonic orders being the Doric and the Corinthian . There are two lesser orders : the Tuscan ( a plainer Doric ) , and the rich variant of Corinthian called the composite order , both added by 16th - century Italian architectural writers , based on Roman practice . Of the three canonic orders , the Ionic order has the narrowest columns . </P>
the doric lonic and corinthian styles are known as the
three classical orders of classical architecture