Qu’est-ce que c’est? is your regular What’s that?, not very formal, but not specially familiar neither.
Qu’est-ce que c’est que ça? is less formal, and bears a sense either of negativity, anger, or surprise. It could be translated into What’s that thing?.
On the other side of the spectrum, you could use the very formal Qu’est-ce? or Qu’est-ce donc?.
Leave a comment