This is the 966th most frequent Icelandic word.
katrín
"Katrín" is the Icelandic form of the name "Katherine," meaning "pure."
In this sentence, 'Katrín' is used as a proper noun, referring to a person's name.
Katrín er að lesa bók.
Katrín is reading a book.
In this usage, 'Katrín' functions as a definite form, identifying a specific individual named Katrín.
Katrínin sem ég þekki er mjög hjálpsöm.
The Katrín I know is very helpful.
Here, 'Katrínu' is the genitive form of 'Katrín', indicating possession (Katrín's place).