1.
book spine; spine of a book
The narrow side of a book visible when it is shelved, typically displaying the title, author, and publisher.
Forms
背 (back) + 表紙 (cover). Note the reading change: 表紙 becomes びょうし in this compound due to rendaku (sequential voicing).
Usage
In Japanese bookbinding, text on the spine traditionally reads from top to bottom. This is relevant when shelving books, as the text orientation differs from Western books.