Another example would be a **Tychonoff** (or Tiknonov, if you prefer) **space**. It can defined, equivalently, as a completely regular $T_0$-space, as homeomorphic to a subspace of some generalized cube (that is, the product space $[0, 1]^S$ for some set $S$, or as homeomorphic to a subspace of a compact Hausdorff space.