Structure

category of sets with finite-to-one maps

Notation Setff\Set_\ff Objects sets Morphisms maps f:X→Yf : X \to Y with the property that for every y∈Yy \in Y the fiber f∗({y})f^*(\{y\}) is a finite set Related FinSet\FinSet, Set\Set
In this variant of Set\Set we only consider maps with finite fibers, which are commonly called finite-to-one. Equivalently, every preimage of a finite set is again finite, and this description makes it obvious that composition is well-defined.

Satisfied properties

Assigned properties

Deduced properties

Unsatisfied properties

Assigned properties

Deduced properties*

*This also uses the deduced satisfied properties.

Unknown properties

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Special objects

  • initial object: empty set
  • coproducts: [finite case] disjoint union

Special morphisms