Topic: Closed Sets, Closure, Interior and Boundary

Why Interior Does Not Preserve Unions

Why Closure Does Not Preserve Intersections

The Open-Neighborhood Criterion for Closure

The Kuratowski Closure Operator

The Interior Operator Laws

Structural Properties of Boundaries

Recovering a Topology from Closure Axioms

Nowhere Dense Sets and Their Criteria

Interior of Arbitrary Unions

Interior of Finite Intersections