This is the 15258th most frequent Polish word.
siostra
"Sister."
Here, "siostra" is used to denote the relation of a sibling, meaning 'sister'.
Moja siostra jest bardzo utalentowana.
My sister is very talented.
In this sentence, "siostra" refers to a professional role, specifically a nurse in a medical context.
Czy widziałeś siostrę w szpitalu?
Did you see the nurse in the hospital?
"Siostra" is used here to describe a member of a religious order, commonly called a nun.