benzene

n. [ From Benzoin. ] (Chem.) A volatile, very inflammable liquid, C6H6, contained in the naphtha produced by the destructive distillation of coal, from which it is separated by fractional distillation. The name is sometimes applied also to the impure commercial product or benzole, and also, but rarely, to a similar mixed product of petroleum. [ 1913 Webster ]

Benzene nucleus,
Benzene ring (Chem.), a closed chain or ring, consisting of six carbon atoms, each with one hydrogen atom attached, regarded as the type from which the aromatic compounds are derived. This ring formula is provisionally accepted as representing the probable constitution of the benzene molecule, C6H6, and as the type on which its derivatives are formed. [ 1913 Webster ]