Already: … rồi, and Rồi as the yes to 'yet?'

Rồi at the end of a sentence means "already": Tôi ăn rồi. I've already eaten. In everyday speech it's the usual way to say something has happened, more common than đã, and the two often go together: Em đã gửi rồi. Rồi comes after the verb and anything that follows it: Tôi mua vé rồi. I've bought the tickets.

It also marks a change, something that's true now and wasn't before: Em hiểu rồi. I get it now. Mưa rồi. It's started raining. Mười giờ rồi. It's ten o'clock already. With sắp or a future time, rồi means it's close or settled, not done: Sắp tới rồi. We're nearly there. Mai em về rồi. I'm going home tomorrow.

Rồi is the yes to a "yet" question. To Em làm bài tập chưa? (Have you done your homework?), answer Rồi or Dạ, rồi for yes, and Chưa for no. Có doesn't work here.

Đúng rồi means "that's right", and you'll hear it all day. After a length of time, rồi means "so far": ba năm rồi, for three years now. Between two actions, it means "and then".