Learn Farsi: این کتاب سی درصد تخفیف دارد. - This book has a thirty percent discount.

The word darsad literally translates to 'in hundred' (dar = in, sad = hundred). To express a percentage, you just place the number directly before this word, exactly like in English. So 'thirty percent' is simply si darsad.

Why does the sentence use the verb darad (has) for a discount?

In English, we often describe a sale by saying an item 'is 30 percent off'. In Farsi, discounts are treated as things an item possesses. We use the verb dashtan (to have), so you literally say 'This book has a thirty percent discount' using darad.

Should the word for discount (takhfif) be plural since we are talking about thirty percent?

No, an important rule to remember in Farsi is that nouns following numbers always remain in their singular form. That is why takhfif stays singular even after the number thirty (si).

Is darsad written as one word or two?

It is written as a single joined word in Farsi, even though its origins come from two separate words. When reading or writing, treat darsad as one complete noun.