Category:Definitions/Countably Infinite

This category contains definitions related to Countably Infinite.
Related results can be found in Category:Countably Infinite.

Countably Infinite Set

Let $S$ be a set.

$S$ is countably infinite if and only if there exists a bijection:

$f: S \to \N$

where $\N$ is the set of natural numbers.

Countably Infinite Class

Let $A$ be a class.

$A$ is countably infinite if and only if there exists a bijection:

$f: S \to \N$

where $\N$ is the set of natural numbers.