没事。

You can use it as a standalone response. If someone bumps into you, just say 没事. If a friend asks if you are busy, say 没事. It works as both an apology-accepter and a status update. In Northern China, people often add an 'r' sound at the end. They say 没事儿 (méi shìr), which sounds a bit more casual and local.

Use it when someone says 对不起 (sorry) for a small mistake. Use it when someone thanks you for a tiny favor. It is perfect for texting when you want to look chill. It also works when you are actually hurt but want to act tough. 'Did you just fall?' '没事!' (even if your knee is scraped).

Do not use it for serious life disasters. If someone crashes your car, 没事 sounds weirdly passive. Avoid using it with very high-ranking bosses in formal reports. In those cases, use 没关系 (méi guān xi) instead. It can also sound dismissive if your tone is too sharp. Don't use it if someone is sharing deep emotional pain. They might think you don't care about their feelings.

Chinese culture often values 'keeping the peace' and social harmony. 没事 helps smooth over the tiny friction of daily life. It shows you are 'da qi' (big-hearted) and not petty. It reflects a cultural desire to not bother others with your problems. By saying 没事, you are maintaining the flow of the social interaction. It is the 'keep calm and carry on' of the Chinese language.

没关系 (méi guān xi) is the slightly more formal cousin. 没问题 (méi wèn tí) means 'no problem' when agreeing to a task. In the south, you might hear 没事情 (méi shì qíng). If you want to be extra polite, add 的 at the end: 没事的. This sounds softer and more comforting, like a warm hug in word form.