Persian, the more widely used name of the language in English, is an Anglicized form derived from Latin *Persianus < Latin Persia < Greek Persis, a Hellenized form of Old Persian Parsa. Farsi is the Arabicized form of Parsi, due to a lack of the /p/ phoneme in Standard Arabic. Native Persian speakers typically call it “Farsi” in modern usage. ISO, the Academy of Persian Language and Literature, and many other sources call the language Persian. The government of Afghanistan uses both “Dari” and “Persian” in English communications.
Communication is generally mutually intelligible between Iranians, Tajiks, and Persian-speaking Afghans; however, by popular definition:
* Tajik could also be considered an eastern dialect of Persian, but, unlike Iranian and Afghan Persian, it is written in the Cyrillic script.