What is the difference between quer and über? Which would I use in the context of going across the river by bus/car/foot?
("quer den Fluss" vs "über den Fluss")
What is the difference between quer and über? Which would I use in the context of going across the river by bus/car/foot?
("quer den Fluss" vs "über den Fluss")
Quer is not a preposition, but something in the direction of an adverb, and because of the given context I have to assume that you falsly used quer as a preposition with an accusative den Fluss. Is my assumption correct?
Alternatively, are you trying to express something in a variant of the language which I am not familiar with? Then you could help by specifying this. I have to assume you're trying to use grammar-book German.
Either way, quer can be used to specify über, emphasizing that you're crossing it. But in my opinion, there is no critical meaning added by not using solely über...
Ich gehe über den Fluss.
Ich gehe quer über den Fluss.
"Quer den Fluss" is possible, but in a way you most likely did not think of. There is not only "quer" (across) but also the Verb "queren", which means to cross something. So
Quer' den Fluß!
would be the Imperativ, a command to cross the river. Admittedly, it makes the most sense grammatically, not really. You will never hear someone say or see someone write that.
What you meant is "über den Fluss" - verbatim "over/across the river". It means "to the other side of the river.
Quer oder über oder beides?
aber:
"über" is a preposition. Hence "über den Fluss" is OK. We don't have a preposition "quer". It is an adverb. "Quer durch den Wald verläuft eine Straße" = "Durch den Wald verläuft quer eine Straße".
"quer den Fluss" would therefore simply be wrong.
Well, unless you are the holy trinity you are not walking on water. Über den Jordan gehen is idiomatic (bibical, "to perish, go south", tbe Jordan being a river as a metaphorical deadline) but über den Fluss gehen is at best outdated and practically not idiomatic. It can quite literally mean to walk over water on a bridge, same as in English, however.
Überqueren "to traverse" is available as a lexicalized phrase, said of large stretches (a busy market place, street in traffic, the sea, a mountain pass). Anything you can singularly step over could instead use gehen, über ~.
Queren also exists as a verb. Although, unless you are a corsair on a crusade, you are not crossing anyone or any of their dominions, compare jemanden übergehen, (eine Grenze) überschreiten.
The essential difference seems to be that über is a proper preposition which quer is not. That is more like an adverb. However, the question is devious. I cannot rule out that dialect maybe uses it like that.
Etymologically, comparison with English queer suggests a sense of going against, as in Querkopf "square, blockhead". This is evident from Querstrebe, a strut which gives structural support under Newton's first law of mechanics.
However, there's a fringe of language contact and analogy in which quer and über might be in part related as fossilized preverb compounds from various parts. That would be a different question. They are clearly distinct in modern German.
"quer" as a geometric relation means misalignment, and "durchqueren" as a verb points out that it's economic to cross a hurdle/river not dwelling too long in it. To make it across the river you build a bridge that runs roughly perpendicular to the flow because everything else is expensive.
If you want to cross the Alps, you say "die Alpen durchqueren" because you don't want to climb through the mountains east-west but rather north-south to save breath and energy. The same for crossing deserts: durchqueren.
"über" is the geometric relation which indicates passing above. So you cannot "überqueren" a river by going through a tunnel. If you pass by swimming or on a horse, this is "durchqueren". If you fly across the Alps in an aeroplane, it's "überqueren." In the history of Hannibal crossing the alps with elephants the standard phrase is "überquerte die Alpen" because it alludes to moving/lifting the heavy animals up and down, so altitude was the issue.