Hereditarily countable set

From Wikipedia, the free encyclopedia

In set theory, a set is called hereditarily countable if it is a countable set of hereditarily countable sets.

Results[edit]

The inductive definition above is well-founded and can be expressed in the language of first-order set theory.

Equivalent properties[edit]

A set is hereditarily countable if and only if it is countable, and every element of its transitive closure is countable.[1]

See also[edit]

References[edit]