Topic: Closed Sets, Closure, Interior and Boundary

Interior as the Largest Open Subset

Exterior and Boundary of a Set

Examples and Nonexamples of Nowhere Dense Sets

Dense Sets and Their Equivalent Criteria

Dense Complements and Nowhere Dense Sets

De Morgan Duality for Closure and Interior

Constructing Dense Sets in Familiar Spaces

Closure of Arbitrary Unions

Closure of Finite Unions

Closure and Interior in Finite Topologies