You seem to have confused sugar with sucrose, also known as table sugar. First off, a carbohydrate, also known as a saccharide, is a molecule composed of one or more monosaccharides. Sugar includes both monosaccharides (e.g glucose, fructose, galactose) and disaccharides (e.g sucrose, lactose, maltose). Sucrose is composed of glucose and fructose, lactose is composed of glucose and galactose, and maltose is composed of two glucose molecules.
Starch, composed of glucose, is the only polysaccharide digestible to humans.
Starch, composed of glucose, is the only polysaccharide digestible to humans.