a form of the book, consisting originally of sheets of parchment or papyrus, and since the late Middle Ages of paper, folded in half and sewn along the fold; groups of sheets were then fastened together on one side. The codex was first widely used in the eastern Roman provinces in the first centuries A.D., replacing tablets and scrolls, and about the sixth century A.D. it became the basic type of book. The adoption of the codex led to the development of binding and of the page and its decoration (page miniature, headpiece). Modern books retain the form of the codex.