basis weight
noun
the weight in pounds of a ream of paper of a basic size, usually 25 × 38 inches (63 × 96 cm) for book stock, 17 × 22 inches (43 × 55 cm) for writing stock, and 20 × 26 inches (50 × 66 cm) for cover stock.
Also called basic weight, basic substance weight.
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019