Iranian Persian in the context of "Farsi"

Persian, also known by its endonym Farsi or Parsi, is a Western Iranian language belonging to the Iranian branch of the Indo-Iranian subdivision of the Indo-European languages. Persian is a pluricentric language predominantly spoken and used officially within Iran, Afghanistan, and Tajikistan in three mutually intelligible standard varieties, respectively Iranian Persian (officially known as Persian), Dari Persian (officially known as Dari since 1964), and Tajiki Persian (officially known as Tajik since 1999). It is also spoken natively in the Tajik variety by a significant population within Uzbekistan, as well as within other regions with a Persianate history in the cultural sphere of Greater Iran. It is written officially within Iran and Afghanistan in the Persian alphabet, a derivative of the Arabic script, and within Tajikistan in the Tajik alphabet, a derivative of the Cyrillic script.

Modern Persian is a continuation of Middle Persian, an official language of the Sasanian Empire (224–651 CE), itself a continuation of Old Persian, which was used in the Achaemenid Empire (550–330 BCE). It originated in the region of Fars (Persia) in southwestern Iran. Its grammar is similar to that of many European languages.

Tajik, Tajik Persian, Tajiki Persian, also called Tajiki, is the variety of Persian spoken in Tajikistan and Uzbekistan by ethnic Tajiks. It is closely related to neighbouring Dari of Afghanistan with which it forms a continuum of mutually intelligible varieties of the Persian language. Several scholars consider Tajik as a dialectal variety of Persian rather than a language on its own. The issue of whether Tajik and Persian are to be considered two dialects of a single language or two discrete languages has political aspects to it.

By way of Early New Persian, Tajik, like Iranian Persian and Dari Persian, is a continuation of Middle Persian, the official administrative, religious and literary language of the Sasanian Empire (224–651 CE), itself a continuation of Old Persian, the language of the Achaemenid Empire (550–330 BC).

The Persian alphabet (Persian: الفبای فارسی, romanized: Alefbâ-ye Fârsi), also known as the Perso-Arabic script, is the right-to-left alphabet used for the Persian language. It is largely identical to the Arabic script with four additional letters: پ چ ژ گ (the sounds 'g', 'zh', 'ch', and 'p', respectively), in addition to the obsolete ڤ that was used for the sound /β/. This letter is no longer used in Persian, as the [β]-sound changed to [b], e.g. archaic زڤان /zaβɑn/ > زبان /zæbɒn/ 'language'. Although the sound /β/ (ڤ) is written as "و" nowadays in Farsi (Dari-Parsi/New Persian), it is different to the Arabic /w/ (و) sound, which uses the same letter.

It was the basis of many Arabic-based scripts used in Central and South Asia. It is used for both Iranian and Dari: standard varieties of Persian; and is one of two official writing systems for the Persian language, alongside the Cyrillic-based Tajik alphabet.

The romanization of Persian is the representation of the Persian language (Iranian Persian, Dari and Tajik) with the Latin script. Several different romanization schemes exist, each with its own set of rules driven by its own set of ideological goals.

Romanization is familiar to many Persian speakers.Many use an ad hoc romanization for text messaging and email;road signs in Iran commonly include both Persian and English (in order to make them accessible to foreigners);and websites use romanized domain names.

Khorasan (Middle Persian: 𐬒𐬊𐬭𐬀𐬯𐬀𐬥, romanized: Xwarāsān; Persian: خراسان, Iranian Persian [xoɾɒːˈsɒːn] ) is a historical eastern region in the Iranian Plateau in West and Central Asia that encompasses western and northern Afghanistan, northeastern Iran, the eastern halves of Turkmenistan and Uzbekistan, western Tajikistan, and portions of Kyrgyzstan and Kazakhstan.

The extent of the region referred to as Khorasan varied over time. In its stricter historical sense, it comprised the present territories of northeastern Iran, parts of Afghanistan and southern parts of Central Asia, extending as far as the Amu Darya (Oxus) river. However, the name has often been used in a loose sense to include a wider region that included most of Transoxiana (encompassing Bukhara and Samarqand in present-day Uzbekistan), extended westward to the Caspian coast and to the Dasht-e Kavir southward to Sistan, and eastward to the Pamir Mountains. Greater Khorasan is today sometimes used to distinguish the larger historical region from the former Khorasan Province of Iran (1906–2004), which roughly encompassed the western portion of the historical Greater Khorasan.

Shirvan (from Classical Persian شروان Shirwān or شیروان Shīrwān [Iranian Persian: شروان Shervân or شیروان Shirvân]; Azerbaijani: Şirvan; Tat: Şirvan) is a historical region in the eastern Caucasus, as known in both pre-Islamic Sasanian and Islamic times. Today, the region is an industrially and agriculturally developed part of the Republic of Azerbaijan that stretches between the western shores of the Caspian Sea and the Kura River, centered on the Shirvan Plain.