# countable

A set is called *countable* if it can be placed into a one-to-one correspondence with some subset of the natural numbers. Thus every finite set is countable, and many infinite sets.

Citation Info

- [MLA] “countable.”
*Platonic Realms Interactive Mathematics Encyclopedia.*Platonic Realms, 10 Apr 2014. Web. 19 Feb 2018. <http://platonicrealms.com/> - [APA] countable (10 Apr 2014). Retrieved 19 Feb 2018 from the
*Platonic Realms Interactive Mathematics Encyclopedia:*http://platonicrealms.com/encyclopedia/countable/