Ik wacht op de bus.
English: I am waiting for the bus.
In Dutch, some prepositions are always used together with specific words or verbs. These are called 'fixed combinations with prepositions'. You have to learn which preposition goes with which word, because it does not always follow a rule.
You use these fixed combinations when you want to connect a verb, noun, or adjective with a preposition in Dutch. The combination is often different from what you might expect. It is important to use the correct preposition with each word.
Ik wacht op de bus.
English: I am waiting for the bus.
Zij denkt aan haar moeder.
English: She thinks of her mother.
Wij praten over het probleem.
English: We talk about the problem.
Hij houdt van muziek.
English: He loves music.
Ik interesseer me voor kunst.
English: I am interested in art.