This is the 8499th most frequent Russian word.
николаевичу
"Николаевичу" is the dative case form of "Николаевич," a patronymic name meaning "son of Nikolay," used to address or refer to someone respectfully.
The word 'николаевичу' is used in the dative case to indicate to whom the book was given, showing a recipient of the action.
Я отдал книгу Николаевичу.
I gave the book to Nikolaevich.
Here, 'николаевичу' is used in the dative case after the preposition 'к,' which indicates motion toward something or someone.
Мы подошли к Николаевичу, чтобы спросить совета.
We approached Nikolaevich to ask for advice.
In this sentence, 'николаевичу' is again in the dative case, representing the person receiving thanks.