Learn Turkish: Buyurun, oturun. - Go ahead, sit down.

The -un suffix is used to give a formal or plural command. In Turkish, when you tell someone to do something, you change the verb ending based on who you are talking to. Here, the speaker is addressing either a group of people, or one person they want to show respect to (like a guest or a customer). If they were talking to a close friend, they would drop the suffix and just say Buyur, otur.

Does "buyurun" always mean "go ahead"?

Not exactly! Buyurun is a very versatile politeness word in Turkish. Depending on the context, it can mean "go ahead," "here you are" (when handing someone an object), "please come in," or "how can I help you?" (when a shopkeeper greets you). Here, paired with the command to sit, it acts as a polite "please, go ahead."

Where is the word for "you" in this sentence?

It is built right into the words! The -un ending on oturun (sit) already tells us that the speaker is talking to the formal or plural "you" (siz). Because the verb ending makes it completely obvious who is being addressed, you do not need to add the word siz to the sentence.