This article outlines the fundamentals of polymer science and emphasizes the aspects that are necessary and useful to applications of engineering plastics. The basic structure of polymers influences the properties of both polymers and the plastics made from them. An understanding of this basic structure permits the engineers to understand which polymers may be acceptable for a certain application, and which may not. There are various possible classification schemes for polymers. Typical classification categories include polymerization process, chemical elements that make up the monomer, or crystalline versus noncrystalline structure. The article describes the various aspects of chemical structure that are important to an understanding of polymer properties and, thus, affect eventual end uses. It discusses different types of names assigned to polymers. The article details the aspects of polymer structure and examines the properties of polymers and the way they are altered by structure.