What term describes prepared ornamental trim in classical architecture?

The term that describes prepared ornamental trim in classical architecture is "entablature." An entablature is a horizontal structure that consists of three main sections: the architrave, frieze, and cornice. It sits atop columns and serves both a decorative and structural purpose in classical buildings. The entablature often features intricate designs, carvings, and moldings that enhance the aesthetic appeal of the architecture, making it a key element in the classical orders such as Doric, Ionic, and Corinthian.

The other options refer to different architectural elements. A capstone typically refers to a finishing stone on the top of a wall or building, serving more of a structural role rather than an ornamental one. Columns are vertical elements that support beams and entablatures but do not specifically refer to ornamental trim. Pillars, much like columns, are vertical structures but can have different connotations in design and style. Understanding the function and appearance of each of these terms clarifies why entablature is the correct answer in the context of ornamental trim.