Ik denk aan mijn vakantie.
English: I am thinking about my vacation.
Fixed prepositional combinations are groups of words in Dutch where a verb, adjective, or noun is always used together with a specific preposition. You cannot change the preposition; it is 'fixed' with the word.
You use fixed prepositional combinations in Dutch when certain verbs, adjectives, or nouns always need a specific preposition to make the meaning complete. You must learn these combinations by heart, because the preposition is not always logical.
Ik denk aan mijn vakantie.
English: I am thinking about my vacation.
Hij wacht op de bus.
English: He is waiting for the bus.
Zij is trots op haar werk.
English: She is proud of her work.
We hebben zin in pizza.
English: We feel like pizza.
Heb jij belang bij dit project?
English: Are you interested in this project?