This is the 6113th most frequent Swedish word.
kerstin
"Kerstin" is a Swedish female given name, equivalent to "Christine" or "Kristin" in English.
In this sentence, 'Kerstin' is used as a proper noun referring to a person's name.
Kerstin älskar att läsa böcker.
Kerstin loves to read books.
Here, 'Kerstin' is again functioning as a proper noun and is used to specify a particular individual in the conversation.
Jag träffade Kerstin på biblioteket igår.
I met Kerstin at the library yesterday.
In this sentence, 'Kerstins' is the possessive form of the proper noun 'Kerstin', indicating ownership.