Chitin is a polysaccharide. A simple linear homopolymer of N-acetyl-D-glucosamine residues is called chitin. Chitin is one of the most abundant substances on earth. It is the second most important polymer in the world. Its chemical symbol is (C8H13O5)n. Numerous D amino monomers are joined by β-1, 4 glycosidic bonds to form chitin.