In
mathematics, the
closure of a subset
S in a
topological space consists of all points in
S plus the
limit points of
S. The closure of
S is also defined as the union of
S and its
boundary. Intuitively, these are all the points in
S and "near"
S. A point which is in the closure of
S is a
point of closure of
S. The notion of closure is in many ways
dual to the notion of
interior.