Breakdown of Poliisin täytyy löytää rikollinen.
löytää
to find
täytyä
to have to
poliisi
the police / police officer
rikollinen
criminal
Questions & Answers about Poliisin täytyy löytää rikollinen.
This lesson is about the passive voice, so why is this necessity sentence here?
It is likely here to remind you of a shared rule! Both the passive voice and necessity verbs (like täytyy) follow the exact same rule for their objects: they take the nominative case (the basic dictionary form) instead of the normal object form ending in -n. That is why the object here is rikollinen, not rikollisen.
Why is the subject poliisin (genitive) and not poliisi?
Sentences expressing necessity (using verbs like täytyy, pitää, or kannattaa) require the subject to be in the genitive case. You can think of the sentence literally as "For the police, it is necessary to find the criminal."
How would I change täytyy if the subject were plural, like "The police officers must"?
You wouldn't change it at all! Necessity verbs like täytyy are "frozen" in the third-person singular form. To say "the police officers must", you simply put the plural subject into the genitive case (poliisien) and leave the verb exactly the same: Poliisien täytyy.
Isn't rikollinen usually an adjective?
It can be both! In Finnish, many adjectives can act directly as nouns. Rikollinen can mean "criminal" as a descriptive adjective, but here it acts as a noun meaning "a criminal". It comes from the noun rikos (a crime).