Farsi is the language most commonly spoken in Iran. It derives from Indo-Iranian language, and it is most commonly called Persian, or Parsi by Western European and North American English language speakers.
As a language, it is separated into several periods of language evolution. Old Farsi or Old Persian was spoken from about 500-300 BCE. Middle Persian dates from about 300 BCE to 800 CE. Modern Persian has been spoken since about 800 CE.
Modern Farsi has influenced many other languages, particularly in the geographic area close to Iran. Ties to it can be noted in Turkish and Azerbaijani, among others. As well, this language is clearly closely related to Hindi.
Farsi has six main vowels and 23 consonants, differing from English alphabets. Nouns as in modern English, lack gender. Farsi tends to structure sentences as subject, prepositional phase, object and lastly verb. This differs from the subject, verb, and object construction of English. Further, it relies most on endings to change words, rather than prefixes. English uses numerous suffixes and prefixes to change meanings, tense, or a word from noun to verb or adjective.
Modern Farsi does show influence by others languages. It may include words from French, English, Arabic and Turkish languages. Especially technical and scientific language can be considered on loan to Farsi.
Some words from Farsi have migrated to the English language. For example the words assassin, angel, lemon, and julep are all derived from this language. More such words migrate into the English language particularly with the use of Fingilish, or Penglish. This is Farsi written with the Latin alphabet. It is commonly used in applications of the Internet, like emails and chats. As well, texting may be done in Penglish.
Farsi clearly influences Arabic since it was once the main language used in trade when the Persian world was preeminent. The Ottoman Empire used Farsi, as did many others. Persian literature, often written in Old or Middle Farsi, is prized by many.