Paper used in furniture design. Watercolor paper has a long history of production and use. The thickness of paper is often measured by caliper, which is typically given in thousandths of an inch in the United States and in micrometers (µm) in the rest of the world. Paper may be between thick. Paper is often characterized by weight. In the United States, the weight assigned to a paper is the weight of a ream, 500 sheets, of varying "basic sizes", before the paper is cut into the size it is sold to end customers. For example, a ream of 20 lb,
Units of paper quantity sheets of vellum or parchment, i.e. 8 leaves, 16 sides. The term "quaternion" (or sometimes "quaternum") designates such a quire. A quire made of a single folded sheet (i.e. 2 leaves, 4 sides) is a "bifolium" (plural "bifolia"); a "binion" is a quire of two sheets (i.e. 4 leaves, 8 sides); and a "quinion" is five sheets (10 leaves, 20 sides). This last meaning is preserved in the modern Italian term for quire, "quinterno di carta". Formerly, when paper was packed at the paper mill, the top and bottom quires were made up of slightly damaged sheets ("outsides") to protect