The dimension of an object is usually thought of in terms of its degrees of freedom or its primary measurement:

• For a Path, it is the Length -> Paths are considered 1D.
• For the Surface, it is the Area -> Surfaces are considered 2D.
• For the Solid, it is the Volume -> Solids are considered 3D.

Paths in 2D and 3D, and surfaces in 3D, can be "pure". An object is pure if it can be enclosed (bounding box) using the same number of dimensions as its degrees of freedom.

• An edge in 2D is pure 1D path, because it needs one dimensionto be enclosed.
• A circle in 2D is not a pure 1D path, because it needs two dimensions to be enclosed.
• A disc in 3D is a pure 2D surface, because it needs two dimensions to be enclosed.
• A sphere is not, because it needs three dimensions to be enclosed.