Breakdown of Ona jest chudsza niż jej siostra.
być
to be
ona
she / it (f)
siostra
sister
jej
her (possessive)
Questions & Answers about Ona jest chudsza niż jej siostra.
How do we form the comparative word chudsza?
It comes from the regular adjective chudy (thin). To make it comparative (thinner), we drop the -y and add the comparative ending. Since ona (she) is feminine, we use the feminine ending -sza. The masculine version would be chudszy.
Why is jej siostra in the basic nominative case here?
When you use the word niż (than) for comparisons, the noun that follows it stays in the same case as the noun you are comparing it to. Since ona is the subject and in the nominative case, jej siostra must also be in the nominative.
Can I use od instead of niż to say "than" in this sentence?
Yes! You can say: Ona jest chudsza od jej siostry. But remember, if you use od (from/than) instead of niż, the noun following it must be in the genitive case. That is why siostra would change to the genitive siostry.
Why doesn't the possessive word jej change its ending to match siostra?
The word jej means "her" (belonging to her). In Polish, jej is actually the genitive form of ona (she) acting as a fixed possessive word. It never changes its spelling to match the noun it describes, regardless of the gender or case of that noun.