intercolumniation defined by Vitruvius as being of the best proportion, i.e. two and a quarter diameters.[28]
• (n.) See Intercolumnlation.
Eu'style` noun [ Greek ..., neut. of ... with pillars at the best distances; ... well + ... pillar: confer French eustyle .] (Architecture) See Intercolumnlation . 
Eustyle is the fifth order of temples, according to Vitruvius, who considered it to be the most elegant; having a space equal to two diameters and a quarter between the columns.
having an intercolumniation of 2 diameters. See illus. under