Nobody, nothing, nowhere: không … ai / gì / đâu

English has single words for "nobody", "nothing" and "nowhere". Vietnamese builds them from không and a question word (ai, gì, đâu), and the word order depends on the job they do in the sentence. After a verb, put không before the verb and the question word after it: Em không biết ai. I don't know anybody. Chị không ăn gì. I'm not eating anything. Hôm nay anh không đi đâu. I'm not going anywhere today.

When "nobody" is the one doing something, không ai goes first: Không ai nói với em. Nobody told me. To say there's nobody or nothing somewhere, use không có ai or không có gì: Nhà không có ai. There's nobody home. For "nothing to …", add để before the verb: Không có gì để ăn. There's nothing to eat.

To make it stronger, like "at all", add hết or cả at the end: Em không biết gì hết. or Em không biết gì cả. I don't know anything at all. Both are used in the North and the South. Some speakers lean one way or the other, but neither belongs to one city.

Không có gì on its own is also the everyday answer to cảm ơn: "You're welcome", literally "it's nothing".

In everyday talk you'll also hear chẳng in place of không, a little more emphatic: Chẳng ai biết. Nobody knows. Tôi chẳng đi đâu cả. I'm not going anywhere.

In a yes/no question, the same question words mean "anyone" or "anything": Em có cần gì không? Do you need anything?