-ene1 Also -diene, -triene, and -ylene.
A variety of common names for hydrocarbons containing a double or triple carbon-carbon bond contain this ending: anthracene, benzene, naphthalene, styrene, toluene, xylene. It is frequently added to the adjectival form of the stem (see -yl): acetylene, ethylene, propylene, allylene, butylene. The artificial fibre called terylene was named by inverting parts of its chemical name (polyeth)ylene ter(ephthalate).
In systematic chemical naming, the -ene suffix is restricted to open-chain (aliphatic) hydrocarbons that contain a double bond: heptene, cyclopentene. Some chemical compounds have both a systematic and a common name: ethene is the systematic name for ethylene, propene for propylene, and so on. The general term for a member of the series, with chemical formula CnH2n, is alkene (German Alkohol, alcohol). The ending -ylene is used in systematic naming only to describe the groups —CH2— (methylene), —C2H4— (ethylene), and —C6H4— (phenylene).
Molecules that contain two double carbon-carbon bonds are named using -diene: butadiene, cyclopentadiene; those that contain three use -triene: hexatriene, cycloheptatriene. Such compounds are known generically as dienes and trienes respectively.