Tu vs. Su usage

Question

Both can mean "your" but when is one used versus the other? Mi casa es su casa, but that could easily be tu casa right? Thank you.

Answer 1

The question is really not about tu and su, but when to use the informal and when to use the formal form.

In general, the tuteo is used with family, friends, people your own age or younger, and people that you are well acquainted with, but the usage is regional. In some countries the formal is only used on solemn occasions and you could properly address a stranger with the informal.

In other regions, the formal is viewed as the more "polite" form and use of the informal with a stranger might seem presumptuous.

The best advice that I've heard is to hang back and observe what is being used before you stick your foot in your mouth. Especially since I would imagine, that the usage may not only be regional, but personal, and you wouldn't want to inadvertantly offend anyone.

So whether it's tu casa or su casa depends on how you are addressing each other. If you're speaking with a child informally then you say tu casa. If he's addressing you you'll probably hear su casa. If you, in turn, address his mother...wait to hear how she addresses you or just politely ask how she would like to be addressed. ¿Puedo tutearte? No, no lo prefiero. (Don't take offense and address her formally.)