Organic compounds got this name because of their association with living organisms. Living matter is predominantly comprised of such compounds that consist mainly of carbon and hydrogen.
Almost all compounds that consist mainly of carbon can be considered organic, the exception being carbides, carbonates, oxides and cyanides, which are excluded for historical reasons.
Compounds classified as organic can be further subdivided into specific classes based on their structures and side groups. For example, aliphatic compounds are usually straight-chain molecules consisting solely of hydrogen and carbon. Aromatic compounds are also composed of hydrogen and carbon but are in a ring-shaped arrangement. Simple organic compounds such as ethylene can be made to bond in very long chains to give polymers, such as polyethylene. Organic compounds can also be classified into natural and synthetic variants, based on their origins.
Natural organics are compounds that are synthesized by plants or animals. Examples include simple sugars, cellulose and vitamins such as B-12. Synthetic compounds do not occur naturally and are prepared by reacting compounds together in a controlled environment. The study of organic compounds, called organic chemistry, is one of the most widely branched subdisciplines of this science. Advances in organic chemistry have made it possible to utilize living organisms to mass produce natural organic compounds such as ethanol and insulin.