Organic compounds are usually classified according to their behavior in chemical reactions, or "functional groups". Examples are alcohols, esters, aldehydes, acids, amines, etc. However, it is not a particular functional group that fibers have in common. What then, is the chemical category that unifies nearly all fibers? That category is "polymers" which are long chain molecules made up of repeating units (monomers) having various functional groups. Here are some polymers that can be used to make textile fibers: * Polyester, in which the monomer is an ester compound, typically the reaction product of ethylene glycol and terephthalic acid. * Rayon (viscose), in which the monomer is d-glucose, a carbohydrate * Nylon-6, in which the monomer is aminocaproic acid, an amino acid