Correct, that’s not a hole in the topological sense. A famous example is a coffee cup: the handle is a (through-) hole, but the inside of the cup is not. As such, the coffee cup is isomorphic (=identical in terms of their overall structure) to a donut.
Correct, that’s not a hole in the topological sense. A famous example is a coffee cup: the handle is a (through-) hole, but the inside of the cup is not. As such, the coffee cup is isomorphic (=identical in terms of their overall structure) to a donut.