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# 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/