"Don't mention it!"
Hmmm. I think we would say pentru nimic as a reply to a thanks, literally translated as for nothing in the sense that it wasn't a big thing to thank for.
However nu e nimic seems like something you would say as a reply to a sorry, literally translated as there's nothing in the sense that it didn't bother you and that it's nothing to worry about.
But they may be used interchangeably, even in other forms, like:
- n-ai pentru ce - literally: you don't have anything (to thank me for / to be sorry about)
- nu face nimic literally: it didn't do anything (for you to thank me / to be sorry about), it may also mean that it doesn't cost anything (in return)
- nu-i nimic literally: there's nothing (to be sorry about)
- n-are nimic literally: it has nothing, but it doesn't make much sense for us either, yet it is used to say that it didn't affect you or bother you as a reply to someone saying sorry
Welp, they are used in various proportions in different regions of Romania. I am not really familiar with what is used in Moldova.
I was trying to come up with an explanation of why that answer was not accepted. The authors perhaps intend to teach the Romanian used in Romania which has slightly diverged from the one in Moldova.