I have seen examples of sentences in German saying: Ich fliege in den Urlaub. Ich gehe zum Einkaufszentrum. Ich gehe ins Bett.
Why is it not, "Ich fliege in dem Urlaub", or "im Urlaub", if the word "in" is used? Isn´t it dative? And why is it "Ich gehe ins Bett" and not "in dem/im Bett" or "zum/zu dem Bett"?
To be honest: The questions related to the causes are difficult to explain. As a German native speaker and non language professional, I don´t care about the rules, but I practice them daily more or less correctly ;-)
- "Ich fliege in den Urlaub." - Question: "In wen oder was fliege ich?" Answer: "In den Urlaub." (Accusative)
- "Ich gehe in das/ins Bett." - Question: "In wen oder was gehe ich?" Answer: "In das/Ins Bett." (Accusative)
"Ich fliege in dem Urlaub." (Dativ = Question: In wem oder was fliege ich?) does not make any sense, because you can´t actively fly in a thing called "Urlaub" ;-)
"Ich fliege in dem Flugzeug." Here you are sitting in an airplane and the airplane is the instrument of transportation, so you have to use Dativ. Same for "Ich fliege mit dem Flugzeug." Question: "In (or: Mit) wem oder was fliege ich?" Answer: "Mit (or: In) dem Flugzeug."
A problem of my explanation is, that a non native German speaker wouldn´t know, which question word he has to use. I German kid knows it naturally.
I found an english website, which adresses this problem and may hopefully help you a bit to understand the german cases:
Ok, "Ich fahre im Urlaub mit dem Rad."
But the meaning changes. "Rad" is Dative here, because it is the instrument used for transportation and it is connected to the preposition "mit".
But I am not sure about the function or case of "Urlaub" in this sentence (maybe also Dative). I think, it means "während des Urlaubs": "Ich fahre während des Urlaubs mit dem Rad." so it is seemingly a temporal indication.
Ok, I found an explanation: Dative is used in connection with some prepositions like "in", "an" and so on. We use Dative to express the place, where an action takes place. In this sentence it is the word "Urlaub", which is not a real place, but I suppose it is a temporal place, where the action "radfahren" takes place.