Questions & Answers about Девушка ждёт трамвай на остановке.
It is in the accusative, but for masculine inanimate nouns, the accusative singular is often identical to the nominative singular.
So:
- трамвай = nominative singular
- трамвай = accusative singular as well
Because ждать takes a direct object, трамвай here is accusative, even though it looks unchanged.
Compare:
- Я вижу трамвай. = I see a tram.
- Я жду трамвай. = I am waiting for a tram.
But with a feminine noun, you would see a visible change:
- Я жду девушку. = I am waiting for the girl.