An -dimensional topological manifold1 is a second-countableHausdorff space that locally resembles -dimensional Real coördinate space,
i.e. every has an open neighbourhood that is homeomorphic to a open subset of . topology
These neighbourhoods are called Euclidean neighbourhoods of the manifold.
Without loss of generality, every point has a neighbourhood homeomorphic to either
an open ball in ; or
the whole of
Thus the so-called Euclidean balls form a topological basis of the entire manifold .
A homeomorphism between a Euclidean neighbourhood and an open subset of is called a chart, and a set of charts covering the whole manifold is called an atlas.
A Transition map allows for the transition between overlapping charts.
Topological manifolds are the most basic kind of Manifold;
every manifold is topologically a manifold.