In this case something like: I want (a thing)=Kérek. I want (the thing)=Kérem. So for example: I want an apple = Kérek egy almát. I want the apple=Kérem az almát. For a somewhat more difficult example involving ice: I would like some ice = Kérek jeget. I would like that piece of ice=Kérem azt a darab jeget.