This is the 727th most frequent Azerbaijani word.
hissəsinin
"Of its part" or "of the part of it."
The word 'hissəsinin' here is used in a possessive case to indicate 'of a part of', specifying a portion of the book.
Kitabın hissəsinin səhifələri cırılmışdı.
The pages of a part of the book were torn.
In this sentence, 'hissəsinin' is used to indicate 'of a part of', referring to a component of the car that requires changing.
Maşının hissəsinin dəyişdirilməsinə ehtiyac var idi.
A part of the car needed to be replaced.
This demonstrates the use of 'hissəsinin' to imply possession, indicating a segment of a larger part, which in this case is part of the house.