This is the 3689th most frequent Polish word.
katarzyny
"Katarzyny" is the plural form of the name Katarzyna, which is the Polish equivalent of the name Catherine.
Here, 'Katarzyny' is used in the genitive case, indicating possession of the book by Katarzyna.
Książka Katarzyny jest na stole.
Katarzyna's book is on the table.
In this sentence, 'Katarzyny' is used to express location or association with a person, here denoting that the action happened at Katarzyna's place.
Byłem u Katarzyny wczoraj.
I was at Katarzyna's yesterday.
The word 'Katarzyny' is again used in the genitive case to denote ownership or association, referring to a diagram made or owned by Katarzyna.