Learn Finnish: Miksi sinä kiität minua?

The verb kiittää (to thank) is a 'partitive verb'. This means the person or thing you are thanking must always be in the partitive case. Because you are thanking 'me', the basic pronoun minä changes to its partitive form, minua.

The dictionary form of the verb is kiittää. Why does kiität only have one 't' in the middle?

This happens because of a spelling rule called consonant gradation. When we conjugate kiittää for sinä (you), the 'closed' ending causes the strong double -tt- to weaken into a single -t-. We then add the personal ending -t for 'you', resulting in kiität.

Can I leave out the word sinä in this sentence?

Yes, absolutely! In Finnish, you can often drop the pronouns for 'I' and 'you'. Because the verb kiität ends with -t, it already clearly means 'you'. Saying Miksi kiität minua? is perfectly correct and very common.

How is the verb kiität related to the common word kiitos (thank you)?

Kiittää is the action verb 'to thank', whereas kiitos is a noun that translates to 'a thank you' or 'thanks'. Since this sentence asks about the action someone is doing ('Why are you thanking me?'), we must use the verb.