Currencies
I just watched a really interesting video on YouTube, but while I was watching it, it kept driving me crazy. :(
In Polish, we say:
- To kosztuje jednego dolara. Kupił to za jednego dolara. It costs one dollar. He bought it for one dollar. || Masculine currency names are treated as animate nouns, so in the accusative they take the same form as the genitive.
- To kosztuję jedną rupię. Kupił to za jedną rupię. It costs one rupee. He bought it for one rupee. || Feminine gender.
- To kosztuje jedno euro. Kupił to za jedno euro. It costs one euro. He bought it for one euro. || Neuter gender.
Here, the declension of the numeral jeden "one".
However, we say:
- To kosztuje jeden złoty. Kupił to za jeden złoty. || Because the name of the Polish currency, złoty, is grammatically an adjective, not a noun.
More at: Które formy są poprawne?
Numerals (including collectives) are the hardest part of Polish grammar for native speakers. As children, we simply didn't need large numbers in everyday life. We learned the rules at school, but, like most kids, we already felt we "knew Polish", so we didn't pay much attention to the finer points of our grammar :(
The biggest problem was that in math class our teachers usually accepted answers written only as symbols. Instead of writing: Dwudziestu pięciu pasażerów wsiadło do pociągu. Twenty-five passengers boarded the train., we simply wrote: 25., and that was perfectly acceptable. Math teachers cared about getting the correct numerical answer, not about how students would express it in proper Polish. We haven't had oral math exams for twenty years, so most younger people rarely have to produce complicated numerals in speech.
So if you're learning Polish, don't worry about making mistakes. Native Polish speakers make them quite often too. That's why we tend to avoid grammatical constructions that we find difficult ourselves. Instead of inflecting numerals like "25" as collective numeral or saying phrases like "1 zł", we frequently use the nouns instead (dwudziestka piątka, złotówka).
Good luck with your Polish