不用客气。

Use it immediately after someone says xiè xie. It is short, rhythmic, and very easy to pronounce. You can say it with a smile and a small nod. In text messages, it is often shortened to just bú kè qi. It works perfectly in almost every daily scenario. Think of it as the 'Swiss Army knife' of polite responses.

Use it when you hold a door for someone. Use it when you lend a pen to a classmate. It is perfect when you give a gift to a friend. If a colleague thanks you for help, this phrase is ideal. It fits beautifully at restaurants when the waiter brings your food. Basically, if someone is grateful, this is your best friend.

Don't use it if someone is apologizing to you. If they say 'sorry,' use méi guān xi instead. Avoid using it with your very strict, traditional boss. In that case, a more formal phrase might be better. Also, don't say it if you are actually angry. It is a warm phrase, so don't waste it on a cold moment. Using it sarcastically is rare and might just confuse people.

The word kè qi comes from the concept of 'guest energy.' In China, guests are treated with extreme, sometimes exhausting, levels of formality. By saying bú yòng kè qi, you are breaking that barrier. You are inviting the person into your inner circle. It shows that helping them was no trouble at all. It is a verbal hug that says 'we are on the same team.'

You will often hear bú kè qi, which is just the shorter version. Some people say bié kè qi, which means 'don't be polite.' In Southern China or Taiwan, you might hear bú huì. If you want to sound extra casual, try méi shì. All of these carry the same 'no problem' energy. Pick the one that feels most natural to your tongue.