How to say "I'm sorry" in Chinese

对不起 is a fixed expression made of 对 (duì, 'toward') and 不起 (buqǐ, 'not up'), literally 'cannot face up to' someone. It's a set phrase, not built from parts you can rearrange.

Use 对不起 for genuine apologies — when you've done something wrong or caused inconvenience. It's polite and formal enough for strangers, but also fine with friends. For a lighter 'excuse me' when passing by, use 借过 (jièguò) instead. Don't overuse it for small favors; that would sound overly dramatic.