Không sao.

• không = not / no
• sao is tricky here. In this expression, it does not mean star. It is part of a common phrase meaning something like a problem, something wrong, or anything the matter.

So Không sao is best learned as a fixed expression meaning:

• It’s okay
• No problem
• Nothing’s wrong
• Never mind

A very literal word-for-word translation is not especially helpful here.

Vietnamese often leaves out things that English requires, especially:

• the subject (it, that, this)
• the verb to be

So instead of saying something like It is not a problem, Vietnamese can simply say:

• Không sao.

This is completely normal and natural. The listener understands the missing subject from the situation.

It is used in several very common situations:

• after someone apologizes

  • Xin lỗi!
  • Không sao.
    = Sorry! / It’s okay.

• to reassure someone

  • Bạn có sao không?
  • Không sao.
    = Are you okay? / I’m fine.

• to say something is not a problem

  • Trễ một chút cũng không sao.
    = Being a little late is okay.

So the exact English translation depends on context.

It can mean both, depending on context.

For example:

• If someone says sorry, then Không sao usually means No problem / It’s okay.
• If someone asks whether you are hurt or whether anything is wrong, Không sao usually means I’m okay / Nothing’s wrong.

This kind of context-based meaning is very common in Vietnamese.

These are related, but they are not always interchangeable.

Không sao

Used for:

• It’s okay
• No problem
• Never mind
• Nothing’s wrong

Không có gì

Often used for:

• It’s nothing
• Don’t mention it
• You’re welcome (in some contexts)

If someone apologizes:

• Không sao sounds very natural.

If someone says thank you:

• Không có gì is more natural than Không sao.

So:

• apology → Không sao
• thanks → Không có gì

It is generally neutral and natural. You can use it in everyday speech with most people.

However:

• by itself, Không sao can sound a little short or plain
• to sound softer or warmer, speakers often say:
  • Không sao đâu.
  • Không sao mà.

These feel more reassuring.

In very formal situations, people might choose fuller expressions, but Không sao is extremely common in normal conversation.

Vietnamese sao has several meanings in different contexts, which can confuse learners.

It can mean:

• star
• how / why / what’s the matter in some contexts
• part of set expressions like không sao

In Không sao, it is best not to think of sao as star. Here it belongs to an idiomatic expression meaning nothing is wrong or no problem.

This is why memorizing the whole phrase is more useful than translating each word too literally.

A rough guide:

• không: sounds somewhat like khong, but with the ng sound at the end
• sao: sounds somewhat like sow in cow, but not exactly

Tone-wise:

• không has the ngang tone, which is level
• sao also has the ngang tone, also level

So both syllables are said with a fairly steady tone:

• không sao

Important note: The kh sound in Vietnamese is not exactly like English k. It is a breathy sound, somewhat like a soft kh or x sound in some languages. But if you say a clear k-like sound at first, people will usually still understand you.

The word đâu often makes the sentence sound softer, more natural, or more reassuring.

Compare:

• Không sao.
  = It’s okay.

• Không sao đâu.
  = It’s really okay / Don’t worry.

So đâu does not completely change the meaning, but it adds a comforting tone.

This is very common in spoken Vietnamese.

Sometimes, but be careful.

If the situation is minor:

• a small mistake
• a light apology
• a small inconvenience

then Không sao is perfect.

But in a serious situation, using only Không sao may sound too light, as if you are minimizing the issue.

For example, if someone is badly hurt or something serious has happened, Vietnamese speakers may use stronger or more specific language instead of just Không sao.

So this phrase works best for:

• everyday reassurance
• small problems
• normal apologies
• saying that nothing is wrong

Yes, very often.

Examples:

• Không sao đâu, bạn cứ yên tâm.
  = It’s okay, don’t worry.

• Trễ một chút không sao.
  = Being a little late is fine.

• Nếu không hiểu thì cũng không sao.
  = If you don’t understand, that’s okay too.

So Không sao is not only a stand-alone reply. It can also be part of a larger sentence meaning it doesn’t matter or it’s not a problem.