noun
opening a book
Refers to the action of opening a book, often used in literary or formal contexts.
開巻の儀を執り行う。
Perform the ceremony of opening a book.
noun
opening part of a book; beginning of a book
Refers to the initial section or opening pages of a book; somewhat formal or literary.
開巻の一節に心を打たれた。
I was moved by a passage at the opening of the book.