1. ISBN (International Standard Book Number): This is a unique 13-digit number assigned to every book publication, regardless of format (hardback, paperback, ebook). It's not specific to paperbacks.
2. Paperback Edition: This refers to a specific version of a book published in a paperback format. It might be a different printing with unique cover art or formatting compared to a previous hardback edition.
3. Library of Congress Control Number (LCCN): This is a unique number assigned to library materials (including books) by the Library of Congress. Again, it's not specific to paperbacks.
4. A specific identifier used by a particular bookstore or online retailer: Some retailers may have their own internal systems for identifying books, and they might use the term "paperback ID" in a specific context.
To understand what "paperback ID" means in your situation, please provide more context:
* Where did you see this term? Was it on a website, in a book, or in conversation?
* What was the context of the term? Were you looking for information about a specific book, or was it in a general discussion about books?
With more information, I can help you understand what "paperback ID" means in your specific case.