A biopolymer composed of (roughly) more than ten monosaccharide residues connected by glycosidic linkages. "Glycan" is synonymous with "polysaccharide" and overlaps in meaning with"oligosaccharide", which refers to a polymer between two and twenty residues in length. They may be branched (such as amylopectin) or linear (such as cellulose and amylose).
Homoglycans contain only one kind of residue, whereas heteroglycans contain two or more different monosaccharides.