Breakdown of Asiakas on tyytyväinen, koska hän tiesi valituksen luetun.
olla
to be
hän
he / she
koska
because
lukea
to read
Questions & Answers about Asiakas on tyytyväinen, koska hän tiesi valituksen luetun.
How does valituksen luetun mean "the complaint had been read"?
This is the past passive referative construction (partisiippirakenne), which replaces an että (that) clause. Instead of saying että valitus oli luettu (that the complaint had been read), Finnish packs it into a shorter phrase. The verb becomes a past passive participle ending in -un/-yn (here, luetun).
Why is the word valitus (complaint) in the genitive form valituksen?
In this construction, the subject of the packed clause (the thing that was read) must be put into the genitive case. So the nominative word valitus takes the -n ending to become valituksen.
Why do we use the passive participle luetun instead of the active lukeneen?
We use the passive form because the complaint did not read anything itself; it was read by someone else. If the sentence was about a specific person reading it, like "she knew the manager had read it", you would use the active participle for the manager: johtajan lukeneen.
How would you say this exact same sentence using a normal että (that) clause instead?
You would say: Asiakas on tyytyväinen, koska hän tiesi, että valitus oli luettu. The referative construction is very common in formal or written Finnish, but thinking of the että version is the best way to understand exactly what the structure means.