Question

I didn't understand和I don't understand有什么区别

Answer 1

他们的解释都对.假如你要表达过去你不明白,你就可以用：

I didn't understand what he said.(昨天你跟一个人聊天,但你听不明白他在说什么.）

I don't understand.指的是现在你对某人/某事/...不明白的时候用.

如果别人说的东西你听不明白,其实可以用:What?/Pardon?会比I don't understand.要好!