Learn Farsi: ممنون، دوست من.

In Farsi, possession is shown by putting the noun first, followed by a connecting sound, and then the pronoun. So دوست (friend) linked to من (I) literally means "friend of me", or "my friend".

Is there a hidden sound between دوست and من?

Yes! There is a short "e" sound connecting them, pronounced as doost-e man. This invisible connector is called the "ezafe". It links a noun to its owner or to an adjective describing it.

I have also heard people say مرسی (mersi). How is ممنون different?

Both are very common ways to say "thank you" in conversational Farsi. ممنون comes from Arabic, while مرسی is borrowed from French. You can use them interchangeably in everyday situations.

Why does the comma look upside down?

The Farsi comma ، points upwards and to the right, which flows better with right-to-left handwriting. It is used just like an English comma to create a pause, such as when addressing someone directly in this sentence.