Books come in different shapes and sizes. They can be tiny..... or massive. To make a book, the printer takes a sheet of paper and folds and cuts it a number of times to produce different sized leaves. A folio is folded once creating two leaves, while a Quarto is folded twice making four leaves. Each leaf size, and hence book size, is given a different name based on the number of folds required. Today publishers can create a book in any size they wish but terms like Folio and Quarto are still widely used. There are dozens of formal names for book sizes but here are a few of the most commonly used ones. Miniature: The smallest books measuring less than 2" in height. Often bibles were printed as miniatures so they could be easily carried, children's books too so they could fit into small hands. Duodecimo: These books measure approximately 5.5" x 7.5" and require four folds of a paper sheet. You will recognize this size as your typical paperback. Octavo: At roughly 6"x9" tall and requiring three folds, the Octavo is a fairly standard size for small hardcover books. Quarto: Folded twice and having a maximum size of about 9.5"x12", you can tell a Quarto by its mostly squarish shape. Folio: At an upward height of 12"x19" the folio is a large upright-shaped book. This format often contain photos, or illustrations Elephant Folio: An oversized folio book 23" to 25" high. Often these will be art books, or atlases, or like this one designed for teachers to read to a large group of children. Learn more about book sizes at AbeBooks: bit.ly/xY96c7