In mathematics, the smallest infinite cardinal number, representing the size of the set of all natural numbers.
From alef/aleph (the first letter of the Hebrew alphabet) + null (from German, meaning zero). A term created by mathematician Georg Cantor in set theory.
Alef-null blew mathematicians' minds when Cantor invented it—there are infinities of different sizes, and alef-null is just the smallest one, suggesting an entire universe of bigger infinities above it!
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