Arabic Mathematical Initial Yeh

It is a yeh-shaped letter used as a distinct mathematical symbol.

In Arabic math notation, this form helps distinguish mathematical symbols from ordinary prose and from one another. It has no universal value: a formula or a book’s convention gives it a role.

Arabic mathematical lettering developed over time rather than through one named invention. The earliest known Arabic algebraic notation in this tradition appears in a Maghrebi arithmetic work by Ibn al-Yāsamīn from the late 12th century; letter shorthand sat alongside written explanation. The style family persisted for centuries in manuscripts and printed handbooks across Arabic-script languages such as Arabic and Persian. Moroccan handbooks used this tradition before French mathematical notation took hold there. That medieval date concerns the notation tradition, not proof that this exact encoded Yeh appeared in the book.

Does this yeh join like an ordinary Arabic letter?

No. It stays a standalone mathematical character.

Ordinary Arabic ي joins neighboring letters and takes a contextual shape. This character already encodes a math style modeled on yeh’s initial shape; Arabic Mathematical Symbols are not reshaped by Arabic joining rules. Use regular ي in running Arabic text.