This is the 186th most frequent Ukrainian word.
якого
"Якого" means "which" or "what kind of" in English, depending on the context.
Used as a relative pronoun referring to 'day', functioning as the object in the subordinate clause.
Це був день, якого я ніколи не забуду.
This was a day that I will never forget.
Used as a relative pronoun referring to 'friend', functioning as the direct object in the subordinate clause.
Я шукаю товариша, якого ви бачили вчора.
I am looking for a friend whom you saw yesterday.
Used as a possessive relative pronoun linking 'book' to its author, showing possession.