The American National Standards Institute, a not-for-profit organization that oversees the creation, promulgation and use of norms and guidelines in a wide range of activities, including paper production and printing.

The dimensions of a ream of paper used to determine basis weight. In the U.S., the basic size for book papers is 25" x 38"; writing papers have a basic size of 17" x 22"; cover papers have a basic size of 20" x 26".

The weight in lbs. of a ream (500 sheets) of paper in the basic size of that grade. Also called substance weight, particularly in bond or business grades of paper.

Originally used to refer to paper used for printing bonds and other certificates, it is now a generic term applied to business papers; also called writing or ledger papers. Bond papers are generally less opaque than an equivalent weight book paper.

The density, or thickness, of a paper measured as pages per inch (ppi). Individual sheet calipers do not necessarily total to ppi, because of how the sheets pack together.

The thickness of a sheet of paper, generally expressed as one-thousands of an inch (0.001"), mils or points.

Short for “picture element.” The smallest individual component of a digital image, usually a colored dot. The greater the number of pixels per inch, the greater the resolution.

An undesirable condition where the printing on the reverse side can be seen through the sheet under normal lighting.