Der Hund ist deiner.
Is this considered to be informal speech; or am I taking things too far and this is considered to be regular speech? Would you say this to your teacher?
we do use it ...sometimes... like for example: you are out with friends then someone brings coffee for everyone in the group, another person was away for some minutes, when he/she comes back someone might say: "der Kaffee da ist übrigens deiner". (by the way, that coffee is yours.)while pointing to the last cup in the middle of the table.
Thanks! Actually, I had to rephrase a good part of my scenario so that it didn't naturally end with "er ist deiner", as this was too close to the information already provided by Mia. That's were a native is invaluable in navigating what's grammaticaly correct, but may or may not be used.