A manifold with boundary of dimension is a topological space
that is a T2-space with a second
countable topology in which every point has a neighborhood homeomorphic to a relatively open
set in the closed half-space
Points represented with form the boundary, which is an
-dimensional manifold
without boundary. The closed ball
is a manifold with boundary whose boundary is a sphere.
For , the same topological conditions apply with local
model
, and the manifold boundary is empty (Lee 2013, p. 27).
A manifold with boundary may have empty manifold boundary. It is then a manifold without boundary (Lee 2013, pp. 26-27).