What is the term for the physical representation of a design concept?

The term that best describes the physical representation of a design concept is "Model." In engineering and design contexts, a model serves as a tangible or visual depiction of an idea or concept, allowing designers and engineers to better understand and communicate their intentions. Models can be created in various forms, ranging from physical 3D representations to simulations or digital constructs. They enable stakeholders to evaluate and refine designs effectively before moving into more costly production stages.

A prototype, while similar, is specifically a working version of a model that is often tested for functionality and use. Blueprints are detailed technical drawings or plans that outline how to construct a design but do not serve as a physical representation themselves. Diagrams typically illustrate concepts or processes through abstract representations rather than providing a concrete form. Thus, "Model" encompasses the broadest scope of physical representation, making it the most accurate choice in this context.