Fol"io (?), n.; pl. Folios (#). [Ablative of L. folium leaf. See 4th Foil.] 1. A leaf of a book or manuscript.

2. A sheet of paper once folded.

3. A book made of sheets of paper each folded once (four pages to the sheet); hence, a book of the largest kind. See Note under Paper.

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

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

6. (Law) 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.

Folio post, a flat writing paper, usually 17 by 24 inches.

Fol"io, v. t. To put a serial number on each folio or page of (a book); to page.

Fol"io, a. Formed of sheets each folded once, making two leaves, or four pages; as, a folio volume. See Folio, n., 3.