# arithmetical hierarchy

> hierarchy which classifies certain sets based on the complexity of formulas that define them

**Wikidata**: [Q669094](https://www.wikidata.org/wiki/Q669094)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Arithmetical_hierarchy)  
**Source**: https://4ort.xyz/entity/arithmetical-hierarchy


## References

1. Freebase Data Dumps. 2013