Final answer:
A fillet is a narrow part of the surface of a column shaft left between adjoining flutes. It helps to define and emphasize the fluting and contributes to the overall decorative quality of the column shaft.
Step-by-step explanation:
A narrow part of the surface of a column shaft left between adjoining flutes is called a fillet. In architecture, a fillet is a narrow, flat, vertical band that separates the flutes of a column. It helps to define and emphasize the fluting and contributes to the overall decorative quality of the column shaft.