KnowraArithmetical hierarchyLinked fromLinked fromThe 5 pages that link to Arithmetical hierarchy, each with the reason it gives.All 5Broader topic 1Related 2Narrower topic 2Computability theoryBroader topic: It refines undecidability into levels of logical and computational complexity.Prenex normal formRelated: Alternations in a prenex prefix help classify formula complexity.Computably enumerable setNarrower topic: Computably enumerable sets form its first existential level.Kőnig's lemmaRelated: Kőnig's lemma underlies reductions between infinite paths and logical definability.Post's theoremNarrower topic: Its Σ⁰ₙ and Π⁰ₙ levels are the theorem's central classifications.