Definition of: folio

(fō′lē·ō, fōl′yō) noun plural ·li·os
1. A sheet of paper folded once or of a size adapted to folding once.
2. A book, or the like, composed of sheets folded but once; hence, a book of the largest size.
3. The size of a book so made up.
4. A page of a book; sometimes, in bookkeeping, two opposite pages numbered alike.
5. Printing The number of a page.
6. Law A certain number of words (72–100), recognized as a unit for estimating the length of a document.
7. A leaf of manuscript or of a book.
8. A holder made of heavy paper for protecting sheets of manuscript, music, etc.
—adjective Consisting of or resulting from a sheet or sheets folded once; having two leaves, hence, four pages.
—v.t. To number the pages or locate the folios of (a book or manuscript) consecutively. [<L, ablative sing. of folium a leaf]