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Aleph null

cardinality of the set of all natural numbers
Aleph-naught, the smallest infinite cardinal number

Aleph null (also Aleph naught or Aleph 0) is the smallest infinite number. It is the cardinality (size) of the set of natural numbers (there are aleph null natural numbers). It is also sometimes called Aleph naught.

It is followed by Aleph one.[1]