This is the 11030th most frequent Polish word.
fińska
"Fińska" means "Finnish" in English, relating to Finland or its language, culture, or people.
In this sentence, 'fińska' is an adjective referring to something from Finland, modifying the noun 'sauna'.
Sauna fińska jest bardzo popularna w Skandynawii.
The Finnish sauna is very popular in Scandinavia.
Here, 'fińską' is the feminine accusative singular form of the adjective 'fiński', describing the noun 'rybę' in the direct object of the sentence.
Kupuję fińską rybę w sklepie ze specjalnościami.
I am buying Finnish fish at the specialty store.
In this instance, 'fińska' functions as an adjective modifying the noun 'kolekcja', indicating that the collection pertains to Finland.