This is the 80th most frequent Serbian word.
којој
"Коjoj" means "to which" or "to whom" in English, used as a dative case of "која" (feminine form of "which" or "who").
Refers to the book as the subject of discussion.
Књига о којој сам ти причала је на полици.
The book I told you about is on the shelf.
Denotes the chair that was leaned upon.
На коју се ученик ослонио била је сломљена.
The chair the student leaned on was broken.
Indicates the woman who was addressed.