# Borel set

> set that can be constructed from open or closed sets by repeatedly taking countable unions and intersections

**Wikidata**: [Q21086747](https://www.wikidata.org/wiki/Q21086747)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Borel_set)  
**Source**: https://4ort.xyz/entity/borel-set