Writing
a small book, a scroll, a written document OR a sheet on which something has been written, i.e., a bill of divorcement
(https://www.biblestudytools.com/lexicons/greek/nas/biblion.html)
It denotes a written document, originally one written on papyrus. Papyrus was rolled (would crack if folded.)
(Origin of the Bible class notes, February 8, 2023. Page 1.)