Polyethylene or polythene is the most commonly produced plastic. It is a polymer, primarily used for packaging. As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. Many kinds of polyethylene are known, with most having the chemical formulaₙ. PE is usually a mixture of similar polymers of ethylene, with various values of n. It can be low-density or high-density and many variations thereof.