CatDat

category of countable sets

A set is countable if it admits a surjection from N\mathbb{N}. In particular, every finite set is countable.

Satisfied Properties

Properties from the database

Deduced properties

Unsatisfied Properties

Properties from the database

Deduced properties*

*This also uses the deduced satisfied properties.

Unknown properties

Special objects

  • terminal object: singleton set
  • initial object: empty set
  • products: [finite case] direct products
  • coproducts: [countable case] disjoint union

Special morphisms

  • isomorphisms: bijective maps
  • monomorphisms: injective maps
  • epimorphisms: surjective maps
  • regular monomorphisms: same as monomorphisms
  • regular epimorphisms: same as epimorphisms