古本

1. Origins, structure, and basic meaning

• Structure: 古本 (ふるほん) is a used or secondhand book.
• Basic usage: 古本屋 forms used bookstore; 古本として売る classifies a finished book as secondhand stock.

2. Common pitfalls and similar expressions

• Bookshop compound and resale category
  • Adding 屋 changes the referent to a store, while として marks the book's resale category; age of the text alone is not decisive.