Aleph symbol

It labels the size of an infinite set.

The first aleph cardinal, aleph-zero (ℵ₀), is the size of the counting numbers; aleph-one (ℵ₁), aleph-two (ℵ₂), and later indices name larger successive cardinalities. That differs from ∞: aleph identifies a set's size, while infinity usually signals unboundedness.

Aleph's story began long before set theory. Its Hebrew namesake belongs to a West Semitic alphabet tradition whose early signs developed in the early second millennium BCE; the name is traditionally linked to an ox. Georg Cantor introduced aleph notation for transfinite cardinals in 1895. The letter stood out in mathematical type, and its name was already associated with one.

Is ℵ the Hebrew letter aleph?

No: ℵ is a mathematical character inspired by Hebrew alef.

In Hebrew writing, א is the first letter, called alef; ℵ is a separate mathematical character that borrows its name and historical connection. In Jewish teaching and mystical interpretation, alef can carry meanings of unity or divine teaching. One interpretation, as described by Chabad, a Jewish religious movement, connects alef's value of one with divine unity and reads its structure as a link among God, people, and the Torah, Judaism's sacred teaching. That tradition-specific reading does not define a set-theory formula.

Why does ℵ look different in different fonts?

The font draws the visible shape; the encoded character stays the same.

Its strokes can look more compact or more like a handwritten Hebrew form in different typefaces. That changes the design, not ℵ's identity.