Persian or Farsi?!
Farsi is the 'Arabized' equivalent for 'Parsi'. Since there is no /p/ sound in Arabic language, the Arabs replaced /p/ of Parsi with /f/ after they invaded Iran. Parsi refers to Persia and means 'of Persia' or 'of Iran', the English version of which is Persian, while 'Farsi' conveys no message about the background of Iran (known as Persia in history).

 Which one do you prefer to say, Persian or Farsi?