[ 'fəʊlɪəʊ ]
■ noun ( plural ~s )
1》 a sheet of paper folded once to form two leaves (four pages) of a book.
↘a book made up of such sheets.
2》 an individual leaf of paper or parchment numbered on the recto or front side only.
↘the page number in a printed book.
Origin
ME: from L., ablative of folium 'leaf', in med. L. used to mean 'on leaf so-and-so'.