Breakdown of Meillä on sellainen kattokruunu, jollainen on nyt hyvin harvinainen.
olla
to be
me
we
nyt
now
hyvin
very
Questions & Answers about Meillä on sellainen kattokruunu, jollainen on nyt hyvin harvinainen.
Why use jollainen here instead of the regular relative pronoun joka?
What case is jollainen in here, and how is that decided?
It is in the nominative case. Just like other relative pronouns, jollainen gets its case from its grammatical role inside the relative clause, not the main clause. Here, it acts as the subject of its own clause (jollainen on... -> "the kind of which is...").
Is sellainen required in the main clause in order to use jollainen?
It isn't strictly mandatory, but sellainen ("that kind of") and jollainen ("the kind of which") form a classic correlative pair. Using them together is very common because it makes the comparison balanced and clearly signals to the listener what kind of descriptive clause is coming next.
Why is hyvin used to mean "very" here instead of tosi or todella?