What term refers to a free or unoccupied area or expanse in architecture?

The term that refers to a free or unoccupied area or expanse in architecture is "space." In architectural terminology, space is understood as the area that lies within the boundaries of a structure, as well as the voids in and around architectural elements. It encompasses not only the physical dimensions but also the experiential qualities that come from how these areas are used and perceived.

Understanding space is fundamental in architecture, as it directly influences how buildings and environments are designed, experienced, and navigated. By manipulating space, architects can shape interactions, facilitate movement, and create atmospheres that respond to human needs and activities.

While other terms like "volume," "base plane," and "spatial dimension" carry specific meanings within architectural discussions, they do not capture the essence of a free or unoccupied area in the same way that "space" does. Volume, for instance, refers to the three-dimensional extent of a form, and base plane denotes foundational elements. Spatial dimension involves measurements and characteristics of space but does not specifically indicate the idea of a swept or empty area. Thus, "space" accurately encompasses the concept of an area that is free or unoccupied in architecture.