CW-complex, Hausdorff space, second-countable space, sober space
connected space, locally connected space, contractible space, locally contractible space
An (open) annulus is a topological space that is homeomorphic to the disk with an interior point removed: $D^2 \setminus \{0\}$.
An often used model for the corresponding closed annulus is the subspace $\{(x,y)\mid 1\leq x^2 + y^2 \leq 4\} \subset \mathbb{R}^2$, of the plane consisting of the point lying between a unit circle and a circle of radius 2, both centred on the origin.