fo

noun

• A leaf of a book or manuscript
• A page of a book, that is, one side of a leaf of a book.
• A page number. The even folios are on the left-hand pages and the odd folios on the right-hand pages.
• A sheet of paper folded in half.
• (books) A book made of sheets of paper each folded in half (two leaves or four pages to the sheet); hence, a book of the largest kind, exceeding 30 cm in height.

  "A rare copy of Shakespeare’s First Folio."

• A page in an account book; sometimes, two opposite pages bearing the same serial number.
• (19th to early 20th century) A leaf containing a certain number of words; hence, a certain number of words in a writing, as in England, in law proceedings 72, and in chancery, 90; in New York, 100 words.
• A wrapper for loose papers.