- a book size of about 6 × 9 inches (16 × 23 centimeters), determined by printing on sheets folded to form 8 leaves or 16 pages. Symbols: 8vo, 8°
- a book of this size.
- in octavo.
- a book size resulting from folding a sheet of paper of a specified size to form eight leaves
- a book of this size
- (formerly) a size of cut paper 8 inches by 5 inches (20.3 cm by 12.7 cm)