The script devised to render Avestan was natively known as "Din dabireh" "religion writing". It has 53 distinct characters and is written right-to-left. Among the 53 characters are about 30 letters that are – through the addition of various loops and flourishes – variations of the 13 graphemes of the cursive Pahlavi script (i.e. "Book" Pahlavi) that is known from the post-Sassanian texts of Zoroastrian tradition. These symbols, like those of all the Pahlavi scripts, are in turn based on Aramaic script symbols. Avestan also incorporates several letters from other writing systems, most notably the vowels, which are mostly derived from Greek minuscules. A few letters were free inventions, as were also the symbols used for punctuation. Also, the Avestan alphabet has one letter that has no corresponding sound in the Avestan language; the character for (a sound that Avestan does not have) was added to write Pazend texts.