Polite Words: ạ, dạ, thưa, xin, mời

Politeness in Vietnamese lives in a few small words rather than in special verb forms.

• ạ closes a sentence to someone older or senior: Cháu chào bà ạ. (Hello, grandma.)
• Dạ or Vâng opens a polite reply, or answers when someone calls you: Dạ, con đây! (Yes, I'm here!)
• Thưa goes before a title to address someone formally, followed by a comma: Thưa thầy, ... (Excuse me, sir, ...)
• xin makes your words humble: xin lỗi (sorry), xin phép (ask permission), Cho tôi xin ... (May I have ...)
• Mời at the start of a sentence invites or offers: Mời anh ngồi. (Please sit down.)

Leaving out ạ and dạ when talking to elders, teachers or customers sounds blunt, so use them often.