The polymer industry is a young industry that has undergone tremendous growth and change over the last sixty years. Many important discoveries in polymer science have been accidental. Most of the learning has been by trial and error and most of the understanding is still basically empirical - make a polymer material or compound and then put it to the test to study what it is and how it performs. This article provides an overview of what polymers and polymer compounds are, why they behave as they do, and it discusses several examples of failures of rubber and plastic components. monomer, polymer, homopolymer, copolymer, terpolymer, viscoelastic, amorphous, thermoplastic, thermoset, plasticizer, vulcanization, modulus, elastic response, entropy, hysteresis, glass transition temperature (Tg), compression set