Final answer:
The term 'mass' in the passage describes the weight, density, and bulk of three-dimensional objects in sculpture and architecture.
Step-by-step explanation:
In the passage, "mass" refers to a term used in the context of three-dimensional objects, such as sculpture and architecture. Here, mass indicates the attributes of weight, density, and bulk of an object. This is important in the visual arts, especially when dealing with the physical form and space that a piece occupies, and how it interacts with its environment.