A mixture of three closely related aromatic hydrocarbons of the benzene group having isomeric forms of orthoxylene (o-xylene), metaxylene (m-xylene), and paraxylene (p-xylene). They each have the formula C6H4(CH3)2 and have close boiling points. They can be separated by crystallization and by distillation. They are important members of the BTX group of petrochemical feedstocks and used in small amounts in aircraft fuel. They are widely used to produce plastics, vitamins, synthetic fibres, dyes, and pharmaceutical products. The non-technical name for xylenes is xylol.