Paranormal space

In mathematics, in the realm of topology, a paranormal space (Nyikos 1984) is a topological space in which every countable discrete collection of closed sets has a locally finite open expansion.

Separation axioms in topological spaces
Kolmogorov classification
T0	(Kolmogorov)
T1	(Fréchet)
T2	(Hausdorff)
T2½	(Urysohn)
completely T2	(completely Hausdorff)
T3	(regular Hausdorff)
T3½	(Tychonoff)
T4	(normal Hausdorff)
T5	(completely normal  Hausdorff)
T6	(perfectly normal  Hausdorff)
History

Not to be confused with paranormal phenomena outside the range of normal experience.

See also

• Collectionwise normal space – Property of topological spaces stronger than normality
• Locally normal space
• Monotonically normal space – Property of topological spaces stronger than normality
• Normal space – Type of topological space – a topological space in which every two disjoint closed sets have disjoint open neighborhoods
• Paracompact space – Topological space in which every open cover has an open refinement that is locally finite – a topological space in which every open cover admits an open locally finite refinement
• Separation axiom – Axioms in topology defining notions of "separation"