The format of any given book is commonly measured by the height and width of a leaf, or page, but because standardized paper sizes did not exist until the beginning of the 20th century, printers and bibliographers utilized a series of specialized terms to understand and measure the sizes of books from across time. This distinct vocabulary describes the size of a book in relation to the number of folds, which transforms the original printed sheets into a body of book pages. Using this terminology, the term ‘folio’ would indicate that the original sheet of paper was folded once, resulting in two leaves. Therefore, a book described as ‘quarto’ would have its original sheet folded twice and would have four leaves. The concept can be extended to ‘octavo’ and ‘duodecimo’, while the number of pages steadily increases and the size of the individual pages tend to become smaller.

The size of such texts can provide insight on its use and value. In addition to being more portable, smaller books can be printed more quickly and use less paper and binding, so they can be sold more cheaply--whereas a book intended to be shown-off, or read by many people at once, is more likely to be produced in a large format. For example, the folio of The Works of Geoffry Chaucer stands over a foot tall, whereas the widely reprinted Familiar letters of Galantes and Others, on all kinds of subjects, a popular guide to writing letters in French, is 6 inches.