This is the 791st most frequent Serbian word.
наставника
The Serbian word "наставника" means "teacher" (male, genitive or accusative singular).
Here, "наставника" is used in the accusative case to denote the object of the action, referring to the teacher being asked.
Упитала сам наставника за додатно објашњење.
I asked the teacher for further explanation.
In this sentence, "наставника" is also in the accusative case, identifying the teacher as the direct object of seeing.
Наставника често видимо на школском игралишту.
We often see the teacher on the school playground.
Here, "наставника" appears in the dative case (used to denote the recipient or beneficiary in this context), referring to the teacher who is the intended recipient of the book.