The International Standard Number (ISN), e.g. International Standard Book Number (ISBN), International Standard Serial Number (ISSN) or any other internationally agreed upon standard number, that uniquely identifies a bibliographic item.

A number used to identify the item in an item group, warehouse or other situation (ex. ISBN – International Standard Book Number, Videorecording Number, etc.) MARC fields: 010, 020, 024, 028, 035, etc.).

a unique number assigned to a periodical or each edition of a book. Since periodicals change title with alarming frequency, the International Serial Standard Number (ISSN), which is constant, is a device that makes locating journals easy. An ISBN (International Standard Book Number) is a unique number assigned to each edition of a title. So the paperback edition of a book will have a different ISBN from the hardback edition.

The ISSN, ISBN, ISN, or any other internationally agreed upon number that identifies an item uniquely.