Plastic is a “polymeric material that has the capability of being molded or shaped, usually by the application of heat and pressure.” Polymers exist in nature—cellulose, for example—but plastics are man-made materials.
http://articles.sun-sentinel.com/2012-11-16/news/fl-palm-public-recycling-20121116_1_blue-bin-jennifer-buce-kate-krebs#.UKfeCQjzptc.mailto