There are more than a way to define the closed set:
In Set Theory: a set is closed under an operation if performance of that operation on members of the set always produces a member of the same set.In Topology: a closed set is a set which contains all its limit points.
Ring topology
An old topology called Token Ring
In point-set topology, the properties of the set S are:X and ∅ belongs to the set S.The intersection of any subsets belongs to the set S.The union of any subsets belongs to the set S.For instance:Let τ = {X,∅}. Then, it's the topology. We call that the trivial or discrete topology. If the set is indiscrete topology, then it contains infinitely many elements!
Ring.
It's called Ring.
There are actually more than a definition of the open set in topology. They are:A set containing every interior point.A set containing a point along the region such that you can form the open ball.
Advantages include: Its easy to set up, handle, and implement, It is best-suited for small networks and its less costly. There 3 types of topology which are; ring, bus and star topology.
Any closed bounded subset of a metric space is compact.
John D. Baum has written: 'Elements of point set topology' -- subject(s): Topology
That is the definition of a closed set.
T. R. Hamlett has written: 'The closed graph and P-closed graph properties in general topology' -- subject(s): Closed graph theorems, Topological spaces