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In [[intuitionistic type theory]] (ITT), a discipline within [[mathematical logic]], '''induction-recursion''' is a feature for simultaneously declaring a type and function on that type. It allows the creation of larger types, such as universes, than [[Intuitionistic type theory#Inductive types|inductive types]], such as [[Intuitionistic type theory#Universe types|universes]]. The types created still remain [[Predicativity|predicative]] inside ITT.
 
An [[inductive definition]] is given by rules for generating elements of a type. One can then define functions from that type by induction on the way the elements of the type are generated. Induction-recursion generalizes this situation since one can ''simultaneously'' define the type and the function, because the rules for generating elements of the type are allowed to refer to the function.<ref name=Dybjer>{{cite journal|last=Dybjer|first=Peter|title=A general formulation of simultaneous inductive-recursive definitions in type theory|journal=Journal of Symbolic Logic|volume=65|issue=2|date=June 2000|pages=525–549|url=http://www.cse.chalmers.se/~peterd/papers/Inductive_Recursive.pdf|doi=10.2307/2586554|jstor=2586554|citeseerx=10.1.1.6.4575|s2cid=18271311 }}</ref>