## You are here

Home$F_\sigma$ set

## Primary tabs

# $F_{\sigma}$ set

A subset of a topological space is called a $F_{\sigma}$ set if it equals the union of a countable collection of closed sets.

The complement of a $F_{\sigma}$ set is a $G_{\delta}$ set.

Related:

G_DeltaSet, G_deltaSet, PavedSet, PavedSpace

Type of Math Object:

Definition

Major Section:

Reference

Groups audience:

## Mathematics Subject Classification

54A05*no label found*

- Forums
- Planetary Bugs
- HS/Secondary
- University/Tertiary
- Graduate/Advanced
- Industry/Practice
- Research Topics
- LaTeX help
- Math Comptetitions
- Math History
- Math Humor
- PlanetMath Comments
- PlanetMath System Updates and News
- PlanetMath help
- PlanetMath.ORG
- Strategic Communications Development
- The Math Pub
- Testing messages (ignore)

- Other useful stuff
- Corrections