The term 'industrial hemp' includes the plant Cannabis sativa L. and any part or derivative of such plant, including seeds of such plant, whether growing or not, that is used exclusively for industrial purposes (fiber and seed) with a tetrahydrocannabinols concentration of not more than 0.3 percent on a dry weight basis. The term 'tetrahydrocannabinols' includes all isomers, acids, salts, and salts of isomers of tetrahydrocannabinols.

Excerpt from https://nifa.usda.gov/industrial-hemp