Folio, Foliation

From Lat. folium = sheet, foliation means the numbering of a manuscript by folios (sheets), not by pages (pagination), which was more common until the 16th century. The folio number was mostly noted at the top of the page. "R" stands for "recto" and means the front ("folio 15r" means "on the front of sheet 15"), "v" stands for "verso" and means the back ("folio 15v" means "on the back of sheet 15").