Breakdown of Wir rühren die Suppe, bis sie abkühlt.
sie
she
wir
we
die Suppe
the soup
bis
until / to (as far as)
Questions & Answers about Wir rühren die Suppe, bis sie abkühlt.
Why is the verb abkühlt at the very end of the sentence?
The word bis (until) is a subordinating conjunction. It introduces a subordinate clause, which means it kicks the conjugated verb all the way to the end of that clause.
Wait, isn't abkühlen a separable verb? Why isn't it split up here?
That's right, it is separable! In a normal main sentence, you would say Die Suppe kühlt ab (The soup cools down). However, because bis pushes the verb to the end of the clause, the two parts of the separable verb reunite and stay together as one word: abkühlt.
Why does the second part say sie abkühlt instead of es abkühlt (it cools down)?
Pronouns in German must match the grammatical gender of the noun they replace. Because soup is feminine (die Suppe), it gets replaced by the feminine pronoun sie, even though we just say "it" in English.
Is the comma before bis mandatory?
Yes. In German, you must always use a comma to separate a main clause (Wir rühren die Suppe) from a subordinate clause (like the one starting with bis).