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 normal Hebrew text, U+05D0 א‎ should be used. U+2135 should be used for the mathematical symbol in Latin-script text because it will share the left-to-right direction of that text.

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