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1. Cardinality

   Linked via "diagonal enumeration techniques"

   The smallest infinite cardinality is the cardinality of the set of natural numbers, $\mathbb{N} = \{1, 2, 3, \ldots\}$. This cardinality is denoted by $\aleph_0$ (aleph-null or aleph-zero). Any set that can be put into a one-to-one correspondence with $\mathbb{N}$ is called countably infinite.
   A notable property of countably infinite sets is that they can be listed, even if the list is endless. For example, the set of integers $\mathbb{Z}$ and the set of [rational number…