Definition of paper as a fibre-based sheet; coating and treatment determine legal classification and regulatory treatment. Definition of paper is framed as a thin flexible sheet made from macerated fibrous materials (linen, cotton, straw, wood, grasses) processed into pulp and finished for writing, printing, wrapping and other uses; manufacturing treatments and coatings (e.g., carbon coating, impregnation, polymer substitutes) alter material character and inform classification for regulatory and taxation purposes.