Definition of "folio" []

• A large sheet of paper folded once in the middle, making two leaves or four pages of a book or manuscript. (noun)
• A book or manuscript of the largest common size, usually about 38 centimeters (15 inches) in height, consisting of such folded sheets. (noun)
• A leaf of a book numbered only on the front side. (noun)
• A number on such a leaf. (noun)
• A page number. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "There is, however, quite a discrepancy in folio numbers from what is cited in Madden and the numbering system currently in place in the manuscript back"
• "English readers, therefore, are driven to the grand edition of the Makámát in folio by Baron Silvestre de"
• "Jean-Félix Watin, “Avis à MM. les souscripteurs de l'in folio de L'Art du peintre, doreur, vernisseur ...” in Supplément (Paris, 1773), 77."