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 × 841 mm). A1 is half the size of a sheet of A0 (i.e., 594 mm × 841 mm), such that two sheets of A1 placed side by side are equal to one sheet of A0. A2 is half the size of a sheet of A1, and so forth. Common sizes used in the office and the home are A4 and A3 (A3 is the size of two A4 sheets). The density of paper ranges from for tissue paper to for some speciality paper. Printing paper is about . Paper may be classified into seven categories: Some paper types include: