This is the 6241st most frequent Turkish word.
çocuğunun
"Çocuğunun" means "of his/her/their child" in English.
The word "çocuğunun" is a possessive form indicating that the child belongs to the mentioned subject, translated as "your child".
Çocuğunun okulda başarılı olması hepimizi çok sevindiriyor.
The fact that your child is successful at school makes all of us very happy.
Here, "çocuğunun" specifies possession, indicating the room belongs to the person's child, i.e., "your child's room."
Bu kitabı çocuğunun odasında buldum.
I found this book in your child's room.
In this context, "çocuğunun" is used to express possession, referring to "his/her child's talents."