Light apologies (everyday)
3For bumping into someone, interrupting, getting attention. Not a real apology, just politeness.
不好意思 excuse me / pardon (everyday "excuse me")
麻烦了 sorry to bother you (when asking for a favor)
打扰了 sorry for the disturbance (entering an office, interrupting)
Standard apologies
3When you actually did something that warrants an apology.
对不起 I'm sorry (standard, sincere)
抱歉 my apologies (slightly more formal than 对不起)
是我的错 it's my fault (explicit acknowledgment)
Strong or formal apologies
3 非常抱歉 sincerely sorry (formal, letters, customer comms)
请原谅 please forgive me (explicit request for forgiveness)
我错了 I was wrong (sincere admission)
Responding to an apology
3 没关系 it's okay (standard)
没事 it's nothing (casual, spoken)
别担心 don't worry (reassuring)