noun pl. folios -·lios′

1. Bookkeeping a page of a ledger, or facing pages with the same number
2. Law a set number of words (100 in the U.S., 72 or 90 in England) considered as a unit of measuring the length of a legal or official document
3. Printing
   1. a large sheet of paper folded once, so that it forms two leaves, or four pages, of a book, manuscript, etc.
   2. a large size of book, about 12 by 15 inches, made of sheets folded in this way
   3. a leaf of a manuscript, book, etc. numbered on only one side
   4. the number of a page in a book, etc.

Etymology: ME < L (in) folio, (in) a sheet, abl. of folium, a leaf (in LL, leaf of paper): see foliate

adjective

transitive verb folioed -·li·oed′, folioing -·lio′·ing