Tehran is the capital and largest city of Iran and also the largest city in Tehran Province. It also serves as the capital of the province, county and the Central District. With a population of around 9 million and 400 thousand in the city and around 16 million and 800 thousand in the larger metropolitan area of Greater Tehran, The Greater Tehran metropolitan area contains towns like the "New Town of Andisheh", "Islam Shahr", "Shahreh Qods", "Shahryar", "Pakdasht", "Firooz Kooh" and "Shamiran". Tehran is the most populous city in Iran and Western Asia, and has the second-largest metropolitan area in the Middle East, after Cairo. It is ranked 24th in the world by metropolitan area population.

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, Dari Persian, and Tajiki Persian. 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.