A type of compound containing hydrogen and carbon atoms arranged in a symmetrical 6-carbon ring structure with single (C-C) and double (C=C) bonds alternating around the ring. Rings are single, multiple or fused and can have other chemical groups attached in place of hydrogen. Benzene, C₆H₆ is the simplest single-ring aromatic, napthalene, C₁₀H₈, the simplest fused-ring aromatic and toluene is the simplest aromatic, having an alkyl side chain, C₆H₅-CH₃. Xylene, a common oilfield chemical, has two methyl side chains, C₆H₄-(CH₃)₂. Aniline is the simplest aromatic amine, C₆H₅-NH₂ and is used in the aniline point test. Aromatic hydrocarbons in oils used to prepare oil-base mud can damage elastomers and increase the toxicity of the fluid. The aniline point test is used for screening oils to infer aromatic content.