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.
- Weisstein, Eric W. "Aleph-0". mathworld.wolfram.com. Retrieved 2020-02-15.