411 REFERENCE · Wiktionary
Lévy hierarchy
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
Etymology
Introduced by Azriel Lévy in 1965.
Proper noun
1
en set theory logic A hierarchy of formulas in the formal language of the Zermelo-Fraenkel set theory. Its first level contains only formulas with no unbounded quantifiers and is denoted by . Subsequent levels are given by finding a formula in prenex normal form which is provably equivalent over ZFC, and counting the number of changes of quantifiers.
en eponyms