Not at all, really: không … đâu

Đâu at the end of a sentence with không makes the "no" firmer and more personal, like "not at all" or "really not": Em không mệt đâu. I'm not tired at all, really. People use it to reassure someone or to put right what they think: Không xa đâu, it isn't far, don't worry.

The phrase you'll hear most is Không sao đâu: it's fine, no problem, don't worry about it. With someone older, add their word: Không sao đâu chị.

It can also turn something down while making clear you mean it: Em không uống đâu. I really won't have a drink. Said warmly, it's friendly; said sharply, it can sound blunt.

This đâu doesn't mean "where": it comes at the end of a "not" sentence (with không, and also with chưa: Em chưa đói đâu, I'm not hungry yet, really), and the sentence isn't a question. Now and then a sentence can be read both ways: Anh không đi đâu is "I'm not going" or "I'm not going anywhere". The situation decides.

In Saigon, đâu có before the verb is a very common, stronger denial: Em đâu có nói vậy! I never said that! That's a later pattern.