Units of paper quantity as ISO 4046. In Europe, the DIN 6730 standard for Paper and Board includes a definition of 1 ream of A4 80gsm (80 g/m) paper equals 500 sheets. The word 'ream' derives from Old French "reyme", from Spanish "resma", from Arabic "rizmah" "bundle" (of paper), from "rasama", "collect into a bundle". (The Moors brought manufacture of cotton paper to Spain.) Early variant rym (late 15c.) suggests a Dutch influence. (cf. Du. "riem"), probably during the time of Spanish Habsburg control of the Netherlands. The number of sheets in a ream has varied locally over the centuries, often according to the
Paper size any size can be made by using sheets of the next larger size, e.g. A4 sheets are folded to make A5 brochures. The system allows scaling without compromising the aspect ratio from one size to another—as provided by office photocopiers, e.g. enlarging A4 to A3 or reducing A3 to A4. Similarly, two sheets of A4 can be scaled down and fit exactly on 1 sheet without any cutoff or margins. The behavior of the aspect ratio is easily proven: on a sheet of paper, let "a" be the long side and "b" be the short side; thus, = . When