Questions & Answers about Ich warte auf ihn.
Why do we use auf here instead of für?
In German, the verb warten (to wait) is almost always followed by the preposition auf to mean "waiting for." Translating word-for-word from English would give you für, but that sounds wrong in German. It helps to memorize them as a pair: warten auf.
Why does auf take the accusative ihn here instead of the dative ihm?
Auf is a "two-way" preposition, which usually takes the dative case for a fixed location and the accusative case for movement. However, when a verb has a fixed, mandatory preposition—like warten auf—it ignores that location rule. Warten auf simply always requires the accusative case, which is why we use ihn (him) rather than ihm.
If I wanted to ask "Who are you waiting for?", how would I say that?
Because you are asking about a person, you combine the preposition with the accusative question word wen (whom). You would ask, "Auf wen wartest du?" (or warten Sie for formal).
What if I want to say "I am waiting for it" (like a bus)? Can I still use auf ihn since Bus is a masculine noun?