This is the 172nd most frequent Serbian word.
јој
The Serbian word "јој" means "her" (dative case) or is an exclamation like "oh" or "alas."
In this sentence, 'јој' is a dative pronoun referring to the indirect object 'her'.
Дала сам јој књигу.
I gave her the book.
In this sentence, 'јој' emphasizes 'her' involvement or relation to the act of her story causing a strong impression.
Њена прича, морам признати, јој ми је оставила јак утисак.
Her story, I must admit, left a strong impression on me.
In this sentence, 'јој' functions as a dative pronoun indicating that the words were directed to 'her'.