Breakdown of Arvaatko salaperäisen kirjeen sisällön?
kirje
letter
arvata
to guess
salaperäinen
mysterious
sisältö
content
Questions & Answers about Arvaatko salaperäisen kirjeen sisällön?
Why is sisältö (content) written here as sisällön?
It is acting as the object of the sentence. Because you are guessing the entire content (a complete action), it takes the total object form, which looks just like the genitive case (ending in -n). Notice how the consonants also soften from lt to ll (sisältö -> sisällön).
If I wanted to say "the content of some mysterious letter", how would I add the word "some" here?
Since a letter is a thing, you would take the pronoun jokin (some/something) and put it in the genitive case to match the rest of the phrase: jonkin salaperäisen kirjeen sisällön. However, in everyday spoken Finnish, it is very common to hear people use jonkun (from joku, normally meant for people) for things too!
What type of verb is arvata (to guess), and how does it become arvaatko?
Arvata is a Type 4 verb (ending in a vowel + ta). To find the stem, you drop the -ta and double the final vowel, giving the stem arvaa-. Then you just add the "you" ending (-t) and the question particle (-ko) to get arvaatko.
Why is the adjective salaperäinen (mysterious) written as salaperäisen?