Xylene is not a single compound, but a mixture of three isomers:

* o-Xylene (1,2-dimethylbenzene): C₈H₁₀

* m-Xylene (1,3-dimethylbenzene): C₈H₁₀

* p-Xylene (1,4-dimethylbenzene): C₈H₁₀

All three isomers have the same molecular formula, but their structures differ in the positions of the two methyl groups (CH₃) on the benzene ring.