Breakdown of Wegen dem Nebel fahren wir langsam.
wir
we
fahren
to drive, to travel
langsam
slow, slowly
wegen
because of
Questions & Answers about Wegen dem Nebel fahren wir langsam.
I thought wegen takes the genitive case. Why is it wegen dem Nebel (dative) here?
You are right that wegen traditionally takes the genitive case (wegen des Nebels), and you should still use that in formal writing. However, in everyday spoken German, it is very common to use wegen with the dative case (wegen dem Nebel).
Could I use weil instead of wegen in this sentence?
Not exactly as written. Wegen is a preposition meaning 'because of' and is followed by a noun phrase (dem Nebel). Weil is a conjunction meaning 'because' and requires a full clause with a subject and a conjugated verb at the end, such as: Weil es neblig ist, fahren wir langsam.
Why is the verb fahren before the subject wir?
German requires the conjugated verb to be in the second position of a main clause. The entire prepositional phrase Wegen dem Nebel takes up the first position, so the verb fahren must come next, pushing the subject wir to the third position.
Why doesn't langsam have an adverb ending here, since it translates to 'slowly'?
In German, the base form of an adjective is also used as an adverb. While English adds '-ly' to change the adjective 'slow' into the adverb 'slowly', German simply uses langsam for both.