Grain (Paper)

The direction in which fibers within a sheet of paper run. 

Depending on the fiber material used in the paper the grain may be different. Fibrous materials like cotton have long fibers which orient themselves in a parralel direction.

Papers may be referred to as both long grain or short grain depending on the cut. If paper grain or fiber of the paper is aligned along the length of the paper or long side, the paper's grain is referred to as grain long. The direction of the grain is important when scoring and/or folding the paper. Scores and folds should always be made in the direction of the paper grain. Some manufacturers denote the grain direction in their lot numbers like Moab so they can provide paper appropriate for special projects.