1. a sheet of paper folded once to make two leaves of a book or manuscript
2. a book or manuscript made of folded sheets; a book of the largest size
3. a page number in a book or manuscript

Examples

• The ancient folio contained handwritten manuscripts from the 16th century.
• She carefully turned each folio in the rare book collection.
• The editor numbered every folio to keep track of the pages.
• The library acquired a first edition folio of Shakespeare's works.
• In botanical terms, a folio is a single leaf of a plant.
• The document was printed on high-quality paper and bound as a folio.