In mathematical logic and descriptive set theory, the analytical hierarchy is an extension of the arithmetical hierarchy. The analytical hierarchy of formulas includes formulas in the language of second-order arithmetic, which can have quantifiers over both the set of natural numbers, N {\displaystyle \mathbb {N} } , and over functions from N {\displaystyle \mathbb {N} } to N {\displaystyle \mathbb {N} } .
In mathematical logic and descriptive set theory, the analytical hierarchy is an extension of the arithmetical hierarchy. The analytical hierarchy of formulas includes formulas in the language of second-order arithmetic, which can have quantifiers over both the set of natural numbers, N {\displaystyle \mathbb {N} } , and over functions from N {\displaystyle \mathbb {N} } to N {\displaystyle \mathbb {N} } .
Source: Wikipedia "Analytical hierarchy" · CC BY-SA 4.0
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