A size of paper (7.5"-10" x 10"-12.5")(190-254 x 254-312 mm), formed by folding and cutting one of several standard sizes of paper (15"-20" x 20"-25")(381-508 x 508-635 mm) twice to form 4 leaves (eight sides).
A book size, corresponding to the quarto paper size.
the size of a book whose pages are made by folding a sheet of paper twice to form four leaves
