The Vietnamese word "gáy sách" refers to the "spine" or "back" of a book. This is the part of the book that is usually visible when the book is placed on a shelf. It holds the pages together and often displays the book's title and author’s name.
In more complex sentences, you might discuss the condition of the "gáy sách." For example, you could say, "Gáy sách của cuốn sách này đã bị rách." (The spine of this book is torn.)
While "gáy sách" primarily means the spine of a book, "gáy" alone can refer to the spine of various objects, not just books. In other contexts, "gáy" can also refer to the nape of the neck in animals, such as a rooster.
In summary, "gáy sách" is a specific term for the spine of a book, used to describe its physical structure and often includes information about the book itself.