A square is a contractible topological space, which implies that it has trivial homology. In particular, they are locally compact, locally connected, first countable, locally contractible, and locally metrizable. As a topological space, it is compact, contractible, path connected and locally path connected. Spaces that are homotopy equivalent to a point are called contractible. One can ask whether "all" contractible manifolds are homeomorphic to a ball. The first is that of homotopy contractible complexes. It follows that all the homotopy groups of a contractible space are trivial. A contractible space is precisely one with the homotopy type of a point. In topology, the plane is characterized as being the unique contractible 2-manifold. For example, an open ball is a contractible manifold. Any fiber bundle over a contractible CW-complex is trivial. Every contractible space is path connected and simply connected. It is path-connected, locally path-connected and simply connected but not contractible. Contractible spaces are not necessarily locally contractible nor vice versa. They are also called contractible types.