International Standard Book Number (ISBN)
A number code used to uniquely identify a published work.
When publishing an e-book, a separate ISBN is required for each e-book file format. (For example, three ISBNs would be required if publishing in EPUB, Kindle format, and PDF.)
The ISBN does not affect copyright, it is merely an indexing number.
» For detailed information, see our article ISBNs and E-Publishing.