Farsi is solely the name of the language. Persian could describe the language or a number of other things, such as the culture, the people, etc. Farsi and Pers

Farsi is solely the name of the language. Persian could describe the language or a number of other things, such as the culture, the people, etc. Farsi and Persian are interchangable in the context of the language, and plenty of Persian Americans prefer using "Persian" to name the language rather than Farsi (this is especially common among persians who refer to themselves as "Persian," and I think a lot of it is because "Farsi" is associated with "Iranian" which has a less ideal connotation associated with it in the West today). But it's not universal, and both are pretty widely accepted. That's my understanding. I'm not versed in the historical details though. There's probably a Persian culture professor lurking who can offer a more informed answer.