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

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.

VG/VG : Very Good Condition book with a Very Good Condition dust jacket. Very Good Condition indicates a used book that does show some small signs of wear - but no tears - on either binding or paper. Any defects must be noted. (as defined by AB Bookman's Weekly).