terpinene

:  any of three liquid isomeric monocyclic terpene hydrocarbons C₁₀H₁₆ obtained usually in mixtures of the alpha and gamma isomers (as by isomerization of pinene, alpha-phellandrene, or dipentene with sulfuric acid): such as a :  the isomer that has an odor like that of lemons and is the principal component of the mixtures and that occurs in coriander oil, chenopodium oil, and other essential oils; 1,3-para-mentha-diene —called also alpha-terpinene b :  the isomer that occurs in coriander oil, lemon oil, and other essential oils; 1,4-para-menthadiene —called also crithmene, gamma-terpinene