Which architectural feature is a rectangular column projecting from a wall?

The correct answer is the term "pilaster," which refers specifically to a rectangular column that is embedded into a wall. This architectural feature typically serves both decorative and structural purposes, often mimicking the look of a classical column but is flatter and attached to a surface rather than standing freely. Pilasters provide a visual element that can enhance the aesthetics of a building while also helping to support the structure.

Columns generally refer to upright, cylindrical supports that can stand alone and have various styles, such as Doric, Ionic, or Corinthian. A post is similar to a column but is usually square or rectangular in cross-section and often serves as a support in different structures. A pillar can be used more broadly to describe a vertical structure providing support but does not specifically denote the rectangular form or the embedded characteristic found in a pilaster. Hence, "pilaster" is the most precise term for a rectangular projection from a wall in architecture.