Learn Farsi: کتاب استاد کجا است؟ - Where is the professor's book?

In Farsi, question words usually stay in the exact same spot where the answer would go. Since the answer (the location) goes right before the verb in a normal sentence, kojâ also goes right before the verb ast (is). The sentence order is literally "Book [of] professor where is?".

How do we know it says "the professor's book" when there is no word for "of" or "'s" written here?

Farsi connects nouns to show possession using an invisible "e" sound called the ezafe. Even though you only see ketâb (book) and ostâd (professor) written side by side, you pronounce it ketâb-e ostâd to mean "the book of the professor".

Is kojâ ast how people normally ask "where is" in everyday conversation?

In formal writing and reading, yes! But in everyday spoken Farsi, the words kojâ (where) and ast (is) almost always get squished together into a single word: kojâst.

There is no word for "the" in front of ketâb (book). Does Farsi not have a word for "the"?

Exactly! Farsi doesn't have a separate, standalone word for "the". A word like ketâb can mean "book", "a book", or "the book" depending on the context. Because we are talking about a specific professor's book here, we naturally translate it using "the" in English.