More like "a key to a door?"
Literally, yes. But "a door key" is more natural, IMO. Just like „klucz od drzwi” is more natural than „klucz drzwiowy”.
It marked it wrong for having no article. An article is only necessary if it's a complete sentence. "Key to the door," by itself is not incorrect!
You're right, added.
And what about: "A key for the door"?
Is the 'do' 100% necessary? Could you instead have 'Klucz' followed by 'drzwi' in the genitive, possessive case?
Is there a genitive case version of the noun 'drzwi'?
Thank you in advance.
The genitive case of "drzwi" is... "drzwi".
"Do" is kinda necessary here, but I can't explain it.
I'd say that "klucz drzwi" would mean that the key belongs to the door the same way as "Michael's key" belongs to Michael.
It is Genitive already because "do" needs it.
It seems similar to English, "key to the door." We don't say "key of the door"
is "Klucz do ten drzwi" correct as "a key to this door" ?