Basis Weight - What does basis weight mean?

Answer:

A measure of weight; basis weight is a more traditional way of measuring the weight of paper (and other materials) and is commonly used in the US.

Basis weight differs from paper density (and grammage) in that it measures paper density in terms of the weight per unit area of a ream of paper that has been cut to a standard size during the manufacturing process. Basis weight is calculated using the mass of the ream, the number of sheets in that ream, and the paper size (each type of paper that is manufactured has its own (different) definition of both the number of sheets in a ream and the standard size) and is expressed as pounds per ream.