Take a cylinder and punch a centered circular hole through it–like a washer. What is that shape called? In 2D it's an annulus, but what's the name of its 3D equivalent?
Also, what is this shape called when you remove part of it along 2 radii?
geometryterminology
Best Answer
Coaxial or annular cylinder.
In a sphere it's a spherical ring. If the remainder of the cutout is round it's a donut or toroid but Wikipedia shows a square toroid too. English.SE has a dozen answers, depending on usage.