speedbump #291: Der Schlüssel (the key)

The German word for 'the key' is 'der Schlüssel'. I don't have a problem with the word itself, but it's the article ahead of it that consistently trips me up. In English one would normally ask, "Do you have the keys?" Translated directly that is "Hast du die Schlüssel?" But Germans don't ask for the keys. They ask for the key. Singular. So the correct question would be "Hast du den Schlüssel?"

This has been quite a bother lately, as a friend of mine is homeless and is staying in my apartment for the week. She doesn't have a key, so we organize our days around our schedules and who has the key when. And so this turns into frequent screw ups.

Unlike other some other linguistic differences, I don't think this one demonstrates a key cultural divergence. Which makes it not very interesting or cool, just something thats been bugging me.

So to recap:
Correct: "Soll ich den Schlüssel mitnehmen, oder nimmst du ihn?"
False: "Verdammte Schlüssel, ich habe sie vergessen."
[To add another layer, that sentence isn't grammatically incorrect. It would just seem strange.]