You may also translate it with: "Watch out, the door!", "Look out, the door!", or "Mind the door!" even "Attention, the door!"
But in my opinion "caution" is also fine. "Caution and attention will be more likely found on a warning sign though.
Whereas: "Careful, the door!" would not be my personal preference, for "Achtung, die Tuer!"
Yeah, this is a literal translation. English speakers would say "mind the door" or "watch the door" / "watch the step" etc.
If we started with "watch out" or "look out", it would be followed by "for" e.g. "watch out for the dog" or "look out for people crossing". To save space, this can be shortened to: "watch out - dog", "look out - people crossing" but we wouldn't shorten to "watch out - the dog" as when shortening, all non-essential words like articles etc. are removed.
Why doesn't caution work here?? I think it should because it basically means the same thing
I answered "Caution, the door!" as well. In hindsight, if we were translating literally, I believe the German phrase would have read "Vorsicht, die Tuer!"
Could this be on sing hanging at the door of laboratory? Like "Caution, Laser Radiation"?