Cardinal Number of Countably Infinite Sets

\(\aleph_0\) (aleph-null)

Explanation

The symbol \(\aleph_0\) (read aleph-null) denotes the cardinality of any countably infinite set. All countably infinite sets — \(\mathbb{N}\), even numbers, integers \(\mathbb{Z}\), rational numbers \(\mathbb{Q}\) — are equivalent to each other and all have cardinality \(\aleph_0\). The symbol \(c\) is reserved for the cardinality of \(\mathbb{R}\) (uncountable).