Learn Finnish: Istuuko mies tuolla? - Is the man sitting there?

The suffix -ko is a question tag that creates a yes/no question. In Finnish, you attach this tag to the word you want to ask about and move that word to the front of the sentence. By attaching it to istuu (sits), the verb becomes the focus of the question.

Why is the question ending -ko instead of -kö?

This is because of vowel harmony. The word istuu has the vowel u, which is a back vowel (along with a and o). When a word contains back vowels, its suffixes must also use back vowels. That is why we use -ko instead of the front-vowel version -kö. The first vowel i is neutral, so it does not interfere with this rule.

Where is the word for "is" in "is the man sitting"?

Finnish does not have an exact equivalent to the English "is doing" structure. The single verb istuu means both "sits" and "is sitting". You do not need a separate word for "is" when talking about an ongoing action!

Why does tuolla end in -lla instead of -llä?

Just like with the question tag, vowel harmony applies here too. The base word is tuo (that), which contains the back vowels u and o. Because of this, the location suffix must be the back-vowel version -lla rather than the front-vowel version -llä.