This is the 874th most frequent Croatian word.
nikola
"Nikola" is a common Croatian male given name, equivalent to "Nicholas" in English.
Here, 'Nikolu' is the accusative case of the name 'Nikola', used to express a direct object in the sentence.
Mog Nikolu nikad nećeš zaboraviti!
You will never forget my Nikola!
In this sentence, 'Nikola' identifies a specific person being introduced and is used as a proper noun.
To je Nikola, moj najbolji prijatelj.
This is Nikola, my best friend.
Here, 'Nikola' is used as a proper noun, specifically a personal name, referring to the subject of the sentence.