linguistic:paraphrasing
Persian alphabet

Modern Iranian Persian and Afghan Persian are written using the Persian alphabet which is a modified variant of the Arabic alphabet, which uses different pronunciation and additional letters not found in Arabic language. After the Arab conquest of Persia, it took approximately 200 years before Persians adopted the Arabic script in place of the older alphabet. Previously, two different scripts were used, Pahlavi, used for Middle Persian, and the Avestan alphabet (in Persian, Dīndapirak, or Din Dabire—literally: religion script), used for religious purposes, primarily for the Avestan but sometimes for Middle Persian.

In the modern Persian script, historically short vowels are usually not written, only the historically long ones are represented in the text, so words distinguished from each other only by short vowels are ambiguous in writing: Iranian Persian kerm "worm", karam "generosity", kerem "cream", and krom "chrome" are all spelled krm (کرم) in Persian. The reader must determine the word from context. The Arabic system of vocalization marks known as harakat is also used in Persian, although some of the symbols have different pronunciations. For example, a ḍammah is pronounced, while in Iranian Persian it is pronounced. This system is not used in mainstream Persian literature; it is primarily used for teaching and in some (but not all) dictionaries.

There are several letters generally only used in Arabic loanwords. These letters are pronounced the same as similar Persian letters. For example, there are four functionally identical letters for / z / (ز ذ ض ظ), three letters for / s / (س ص ث), two letters for / t / (ط ت), two letters for / h / (ح ه).On the other hand, there are four letters that do not exist in Arabic پ چ ژ گ.