Closure
From Conservapedia
In topology, the closure of a set is the intersection of all closed sets containing . Equivalently, the closure of is the union of and all limit points of
A closure operator is an abstract (category theory) form of the topological notion of closure which can be applied to any set . It is a function from to the power set of satisfying the following conditions:
- (augmentation)
- If then (monotonicity)
- (idempotence)
In the category of topological spaces, this operator is isomorphic to the standard topological one.