The most important case in Turkish. The possessive case : ) ) )

ım, im, um, üm > my

ın, in, un, ün > your

ı, i, u, ü > his/her/its

It is not a case. At least not a grammatical case.

Even so, case is the best word to define it.

I think they are called possessive suffixes. That´s a better name.