(ISBN) is a unique identifier assigned to books, audiobooks, eBooks, and other types of published media. The ISBN is a 10- or 13-digit number that is used to identify a specific edition of a book and distinguish it from other editions. The purpose of ISBN is to ensure that each published work can be easily located and identified, and to simplify the ordering process for libraries, bookstores, and other institutions. The ISBN is typically printed on the back cover of a book or on the copyright page. It's important to note that an ISBN is unique to a specific edition of a book and will change if any aspect of the book changes, such as the cover design, format, or contents.