A simplified, freeform 3D shape used in Revit's conceptual design environment to explore a building's overall form and massing - footprint, height, setbacks - before committing to real walls, floors, or roofs. Faces of a mass can be converted directly into actual building elements once the form is settled, so early massing work is not thrown away, it becomes the starting geometry for the real model.

Massing is also where a lot of early 6D analysis happens - solar studies, floor-area calculations, shadow studies - because it lets a design team test many volumetric options quickly, before the cost of full detailed modeling makes changes expensive.