What does a prostyle column refer to in architecture?

A prostyle column refers to a portico of columns situated at the front of a building, typically supporting a roof and creating an entrance that is visually impactful. This architectural feature is common in Classical architecture and is often used to convey a sense of grandeur and order. The arrangement emphasizes the façade of the building, drawing attention and creating a ceremonial approach.

The other options do not accurately describe the concept of a prostyle column. While a building entirely constructed of columns might relate to other architectural styles or structures, it does not specifically encapsulate the idea of a prostyle. A decorative column without support misses the functional aspect of classical columns, which are typically both decorative and structural. Lastly, a single column supporting a roof does not fit the definition of a prostyle, which involves multiple columns organized into a unified arrangement at the entrance rather than just one. Thus, the definition of a prostyle column is best encapsulated as a portico of columns on the front of a building.