Go on, do it / let's: verb + đi

Đi at the end of a sentence urges someone to go ahead and do something: Ăn đi! Go on, eat! Anh ngồi đi. Have a seat. It's friendly and direct, like "go on" or "go ahead", and it's what you say when you offer someone food or a seat. How it sounds depends on who you're talking to: with someone older, add their title (Bác ngồi đi), or use mời to be safe: Mời bác ngồi.

With mình or chúng ta (we) in front, it means "let's": Mình đi uống cà phê đi! Let's go for a coffee! If there's an object, đi comes after it: Uống nước đi. After đi you can still add the person's title or nha: Uống nước đi em.

It's also how people bargain at the market: Bớt cho em chút đi chị. Could you knock a bit off?

This is the same word as đi, "go", but at the end of a sentence it doesn't mean going anywhere. That's why Đi đi! simply means "Go on, go!"

Đừng is the opposite: "don't". Nha at the end (in Hà Nội, nhé) is softer, more of a suggestion: Mình đi ăn nha? The two often go together: Ăn đi nha. Hãy, which you'll see on signs and in instructions, is more formal.