-ene¹

Also ‑diene, ‑triene, and ‑ylene.

Hydrocarbons.

Greek ‑ēnos.

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 C_nH_2n, 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.