a leaf of a book or manuscript

A page of a book, that is, one side of a leaf of a book.

(printing) A page number. The even folios are on the left-hand pages and the odd folios on the right-hand pages.

(paper) 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.

(accounting) A page in an account book; sometimes, two opposite pages bearing the same serial number.

A wrapper for loose papers.

to put a serial number on each folio or page of (a book); to page