Questions & Answers about Mihin heidän bussinsa menee?
Why do we need both heidän and the -nsa suffix here?
In Finnish, third-person possessives like "his", "her", or "their" require double marking. You must include the genitive pronoun (heidän) before the word, and also attach the possessive suffix (-nsa or -nsä) to the end of it. This is different from first and second person, where the pronoun (like minun) can often be dropped.
Why does the suffix end in -a (bussinsa) instead of -ä?
This is because of vowel harmony. The word bussi contains the back vowel u. Because it has a back vowel, it requires the back-vowel version of the possessive suffix, which is -nsa.
Why is "where" translated as mihin instead of missä?
Mihin specifically means "where to", while missä means "where at" or "in where". Because the verb menee (goes) expresses movement toward a destination, you have to use the directional question word mihin.
Why is the verb menee singular if heidän means "their"?