Ktav Ashuri

According to Halakha (Jewish religious law), tefillin (phylacteries) and mezuzot (door-post scripts) can only be written in Ashurit.

Consequently, the term Ktav Ashuri refers primarily to a traditional calligraphic form of the alphabet used in writing the Torah.

[1] However, the term Ashuri is often used in the Babylonian Talmud to refer to the contemporary "Hebrew alphabet", as opposed to the older Paleo-Hebrew script.

[2] The Talmud gives two opinions for why the script is called Ashuri: The name reflects the fact that the Hebrew alphabet used by Jews (as opposed to the Samaritans) was derived from the Aramaic alphabet (Hebrew: אלפבית ארמי) used in Assyria and Babylonia and Imperial Aramaic was a lingua franca of both states' empires, it thus refers to "the Aramaic alphabet as used in Judaism",[5][6] and is sometimes referred to as the "Assyrian script."

[7] Mention of the Ashuri script first appears in rabbinic writings of the Mishnaic and Talmudic periods, referring to the formal script used in certain Jewish ceremonial items, such as sifrei Torah, tefillin, mezuzot, and the Five Megillot.