Organic compound, simplest member of the class of phenols. A colourless liquid with a bland, sweetish odour, it is toxic and caustic. It is a high-volume industrial chemical used chiefly in the manufacture of phenol-formaldehyde resins (seeformaldehyde; plastics), epoxy resins, nylon, herbicides, biocides, other synthetic chemicals and pharmaceuticals, and dyes. It is also a solvent and general disinfectant. The phenol coefficient is a number that expresses the germicidal action of a chemical compared with that of phenol.