DJ : Short for dust jacket, a protective and often decorative wrapper, usually made of paper which wraps around the binding of a book.

endpaper : The double leaves bound into a book at the front and rear after printing. One side is glued to the inner portion of the boards (the paste-down) and the other is left loose (free endpaper).

4to : Or quarto. A term used generally to describe the approximate size of a book, a book that is about 10" to 12" tall and roughly squarish in shape. The term is based on the size of paper traditionally used by book printers which has been folded and cut into 16 pages.