Chitin is a long-chain polymer derived from glucose that forms part of the hard outer exoskeleton in insects, crustaceans, fungi, and other organisms.
Exoskeleton: An external skeleton that supports and protects an animal's body in contrast to the internal skeleton (endoskeleton) of humans.
Polymer: A large molecule composed of many repeated subunits known as monomers.
Glucosamine: An amino sugar that is an essential component of chitin.