Learn Finnish: Miksi sinä olet väsynyt tänään?

In Finnish, question words like miksi simply go at the beginning of the sentence, and the rest of the words keep their normal statement order (subject + verb). You don't need to flip the subject and verb like you do in English! Literally, this sentence is structured as "Why you are tired today?".

Do I have to include the word sinä?

No, you can drop it! The verb ending -t in olet already tells us the subject is "you". Saying Miksi olet väsynyt tänään? is perfectly correct and actually very common in everyday Finnish.

Does the word väsynyt change depending on who is tired?

If you are talking about one person, it stays exactly the same. For example, "Why is he tired?" is Miksi hän on väsynyt?. However, if you are asking about multiple people (like "Why are we tired?"), it takes a plural ending and becomes väsyneitä.

Does the time word tänään have to go at the very end of the sentence?

Not necessarily. Finnish word order is quite flexible. While putting the time at the end is very natural and common, you could also say Miksi sinä olet tänään väsynyt?. The meaning stays the same, it just slightly shifts the focus of the sentence.