Natural oil with a distinctive scent secreted by the glands of certain aromatic plants. Terpenes are the main constituents.

Essential oils are extracted from plants by steam distillation, extraction with cold neutral fats or solvents (e.g. alcohol) or pressing and used in perfumes, flavourings and medicine; e.g., citrus oils, flower oils (e.g. rose, jasmine) and oil of cloves.