Learn Romanian: Mersi pentru cafea! - Thanks for the coffee!

Yes! Romanian borrowed mersi from French, and it is incredibly common in daily life. It is used as an informal 'thanks' with friends, family, and colleagues, whereas mulțumesc is the standard or slightly more formal 'thank you'.

The English translation says 'for THE coffee', but cafea doesn't have the definite article attached. Why not cafeaua?

In Romanian, when a noun directly follows the preposition pentru (for), it usually stays in its basic dictionary form. You drop the definite article unless you are describing the noun further, like in the phrase pentru cafeaua fierbinte (for the hot coffee).

What if I want to thank them for multiple coffees?

The plural of cafea is cafele. Because the rule for the preposition pentru stays the same, you would simply swap the word and say Mersi pentru cafele! without adding the plural definite article.

What is the most natural way to reply to this?

The standard reply to 'thank you' in Romanian is cu plăcere (with pleasure). Another great option here is pentru puțin (literally 'for a little'), which is the Romanian way of saying 'don't mention it' or 'it was nothing'.