Canvas is described as a tightely woven cloth used for sails, covers, dodgers and biminis. Typically made from cotton, hemp or linen. Sailcloth made out of synthetic materials are now used for modern sails.
See also:
"Canvas" is in the NAICS Code "31491"
(Textile Bag and Canvas MillsTextile Bag and Canvas Mills)
"Canvas" is in the HS Code "5907"
Textile Fabrics Otherwise Impreganted, Coated Or Covered; Painted Canvas Being Theatrical Scenery; S
"Canvas" is in the UNSPSC Code "24111501"
Canvas bags
Ref: 122254/2006-10-09