The terpinenes are a group of isomeric hydrocarbons that are classified as terpenes. They each have the same molecular formula and carbon framework, but they differ in the position of carbon-carbon double bonds. α-Terpinene has been isolated from cardamom and marjoram oils, and from other natural sources. β-Terpinene has no known natural source, but has been prepared synthetically from sabinene. γ-Terpinene and δ-terpinene (also known as terpinolene) are natural and have been isolated from a variety of plant sources.