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countable (Definition)

A set $ S$ is countable if there exists a bijection between $ S$ and some subset of $ \mathbb{N}$.

All finite sets are countable.



"countable" is owned by vampyr.
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See Also: proof that the rationals are countable, Cantor set


Attachments:
subsets of countable sets are countable (Corollary) by beke
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Cross-references: finite sets, subset, bijection
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This is version 2 of countable, born on 2001-11-16, modified 2002-02-27.
Object id is 880, canonical name is Countable.
Accessed 15663 times total.

Classification:
AMS MSC: 03E10 (Mathematical logic and foundations :: Set theory :: Ordinal and cardinal numbers)
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