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). Georg Cantor invented and named the concept.

It is the first infinite number in a series of infinite cardinal numbers. The symbol for aleph null is ℵ0.

It is followed by aleph one.[1]


  1. Weisstein, Eric W. "Aleph-0". Retrieved 2020-02-15.