Folio:

• In bookbinding, a sheet of paper, parchment, or other material folded in half to make two leaves in a codex.
• A sheet of paper, parchment, or other material used as a single leaf in a codex.
• A book bound from folio sheets, usually 15" tall or more; see bookbinding.
• Any unusually large and noteworthy book edition, such as the First Folio of William Shakespeare.
• Software by NextPage Inc. for cross-platform publishing.