This is the 912th most frequent Serbian word.
њихови
"Their" (possessive pronoun).
The word 'њихови' is used as a possessive pronoun denoting ownership, referring to something belonging to 'them'. Here, it refers to the possessiveness of the dogs.
Њихови пси трче по парку.
Their dogs are running in the park.
In this sentence, 'њихови' is used similarly as a possessive pronoun, indicating that the house mentioned belongs to 'them' (a group of people).
Видела сам њихови кућу јуче.
I saw their house yesterday.
Here, 'њихови' functions as a possessive pronoun modifying the noun 'пријатељима' (friends), showing that these friends are associated with 'them' (the owners).