The topological closure of a set 
in a topological space
is the smallest closed set containing 
. Closed sets are closed
under arbitrary intersection, so it is also the
intersection of all closed
sets containing 
.
Equivalently, it is 
together with all of its limit points.
Topological Closure
See also
Closed Set, Sequence, Set Closure, TopologyThis entry contributed by Todd Rowland
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Cite this as:
Weisstein, Eric W., with contributions by Todd Rowland. "Topological Closure." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/TopologicalClosure.html