Is there a proper name for a shape defined by the volume between two concentric spheres? My understanding is that, formally, a "sphere" is strictly a 2D surface and there's a formal term for volume contained by that surface -- which I forget.
Is there a term that describes the volume between two concentric spheres? That is, colloquially, a "a filled in sphere with a hollow core".
Another phrasing would be, what is the name for a three dimensional annulus? (Or is an annulus not strictly two dimensional?)