Arabic mathematical teh

It is Arabic teh used as a mathematical letter.

In algebra, it can name a variable. A Mashreq (Middle Eastern) example from 2006 uses teh as the sign for a function, from Arabic تابع (tābiʿ, “function”). A Maghreb (North African) example uses the Arabic letter dal (د) for that role.

The letter style behind Arabic mathematical forms comes from an Arabic alphabet variant used in manuscripts and printed books for centuries. Maghrebi algebraic symbols were in use by the late 12th century. A manuscript found on Jerba, a Tunisian island, is a copy of a commentary written in 1380; it was completed in Istanbul in 1747, and its margins contain many mathematical symbols.

Why doesn’t 𞸕 join like Arabic text?

Arabic mathematical symbols do not join like ordinary Arabic letters.

Ordinary ت is a letter in running Arabic; it changes shape to connect to neighboring letters. 𞸕 is an encoded math character that keeps its form instead. Typing ت in a formula may therefore trigger Arabic joining.

Arabic mathematical styles can signal different mathematical meanings too. An initial form or a stretched form is its own math character, so a font’s bold or italic setting is not a substitute.