---
tag: E7WEFRMQTB
kind: concept
name: Buchholz psi functions
aliases: [buchholz-psi-function]
sources:
  - wikipedia: en:54183426@r1346942673
    locator: Buchholz psi functions
    note: adopted
    mention: wikipedia://en/54183426
    sections: [Summary]
same_as:
  wikidata: Q48996114
  wikipedia: Buchholz psi functions
inventory: [5SXQMWDD1X]
---

## Summary

**Buchholz's psi-functions** are a hierarchy of single-argument ordinal functions $\psi_\nu(\alpha)$ introduced by German mathematician Wilfried Buchholz in 1986. These functions are a simplified version of the $\theta$-functions, but nevertheless have the same strength as those. Later on this approach was extended by Jäger and Schütte.