ISBN (International Standard Book Number)
A unique numeric identifier for books, used internationally. ISBN-13 is the current standard with 13 digits, while older books may have 10-digit ISBN-10.
Why it matters
ISBNs allow you to unambiguously identify a specific edition of a book, which is critical when different editions have different page numbers or content. Using an ISBN ensures your readers can locate the exact version you referenced, preventing confusion between hardcover, paperback, or revised editions.
How to use
You can find a book's ISBN on the copyright page, the back cover near the barcode, or in library catalog records. While most citation styles do not require the ISBN in the reference entry, it is invaluable for looking up the book's full metadata when building your citation.
In academic writing
Students most often use ISBNs when citing textbooks, edited volumes, and monographs. Library databases and citation tools accept ISBNs to auto-generate complete reference entries. When your professor assigns a specific edition of a textbook, the ISBN is the fastest way to confirm you are citing the correct version.
Common mistakes
- •Using the ISBN from a different edition of the book than the one actually consulted.
- •Confusing ISBN-10 and ISBN-13 formats — both refer to the same book but ISBN-13 is the current standard.
- •Including the ISBN in the formatted citation when the style guide does not require it.
Example
978-3-16-148410-0
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