ℵ

Introduced by Georg Cantor, based on the Hebrew letter א‎, initial letter of אינסוף (infinity).

ℵ (English symbol name aleph)

1. (set theory) Symbol for the transfinite enumeration of the infinite cardinal numbers in order of magnitude, a function mapping ordinal numbers to infinite cardinals.

• Unicode has two code points for the Hebrew letter aleph. For Hebrew text, א‎ should be used. This character should be used for the mathematical symbol since it retains the left-to-right orientation of the text.

• ℵ₀: aleph-null, aleph-zero
• ℵ₁: aleph-one
• ℶ