What is "intercolumniation"

Intercolumniation \In`ter*co*lum`ni*a"tion\, n. (Arch.) The clear space between two columns, measured at the bottom of their shafts.
--Gwilt.

Note: It is customary to measure the intercolumniation in terms of the diameter of the shaft, taken also at the bottom. Different words, derived from the Greek, are in use to denote certain common proportions. They are: Pycnostyle, when the intercolumniation is of one and a half diameters; Systyle, of two diameters; Eustyle, of two and a quarter diameters; Diastyle, of three diameters; Ar[ae]ostyle, of four or more, and so great that a wooden architrave has to be used instead of stone; Ar[ae]osystyle, when the intercolumniations are alternately systyle and ar[ae]ostyle.

In architecture, intercolumniation is the spacing between columns in a colonnade, as measured at the bottom of their shafts. In classical, Renaissance, and Baroque architecture, intercolumniation was determined by a system devised by the first-century BC Roman architect Vitruvius. Vitruvius compiled standard intercolumniations for the three classical Greek orders, expressed in terms of the column diameter, twice the Vitruvian module, and he warned that when columns are placed three column-diameters or more apart, stone architraves break.