The Persian alphabet () is the right-to-left alphabet used for the Persian language. It is a modification of the Arabic alphabet with four additional letters added: چ پ ژ گ. It was the basis of many Arabic-based scripts used in Central and South Asia. It is used for the Iranian and Dari standard varieties of Persian; and is one of two official writing systems for the Persian language, along side the Cyrillic-based Tajik alphabet. The script is mostly but not exclusively right-to-left; mathematical expressions, numeric dates and numbers bearing units are embedded from left to right. The script is cursive, meaning most letters in a word connect to each other; when they are typed, contemporary word processors automatically join adjacent letter forms. History The Persian alphabet is directly derived and developed from the Arabic alphabet. The Arabic Alphabet was introduced to the Persian-speaking world after the Muslim conquest of Persia and the fall of the Sasanian Empire in the 7th century. Following which, the Arabic language became the principal language of government and religious institutions in Persia, which led to the widespread usage of the Arabic script. Classical Persian literature and Poetry were affected by this simultaneous usage of Arabic and Persian. A new influx of Arabic vocabulary soon entered the Persian language. In the 8th century the Tahirid dynasty and Samanid dynasty officially adopted the Arabic script for writing Persian, followed by the Saffarid dynasty in the 9th century, gradually displacing the various Pahlavi scripts used for the Persian language prior. By the 9th-century the Perso-Arabic alphabet became the dominant form of writing in Greater Khorasan. Under the influence of various Persian Empires, many languages in Central and South Asia that adopted the Arabic script use the Persian Alphabet as the basis of their writing systems. Today, extended versions of the Persian alphabet are used to write a wide variety of Indo-Iranian languages, including Kurdish, Balochi, Pashto, Urdu, Punjabi, Saraiki, Sindhi and Kashmiri. In the past the use of the Persian alphabet was common amongst Turkic languages, but today is relegated to those spoken within Iran, such as Azerbaijani, Turkmen, Qashqai, Chaharmahali, and Khalaj. With the Uyghur language in western China being the most notable exception. During the colonization of Central Asia many languages in the Soviet Union, including Persian, were reformed by the government. Ultimately resulting in the Cyrillic-based alphabet used in Tajikistan today. See: . Letters Below