: any of a large class of volatile odoriferous oils of vegetable origin that give plants their characteristic odors and often other properties, that are obtained from various parts of the plants (as flowers, leaves, or bark) by steam distillation, expression, or extraction, that are usually mixtures of compounds (as aldehydes or esters), and that are used often in the form of essences in perfumes, flavorings, and pharmaceutical preparations—called also ethereal oil, volatile oil; compare fatty oil, fixed oil
Any of a class of highly volatile (readily evaporating) organic compounds found in plants and usually named for them (e.g., rose oil, peppermint oil). They have been known and traded since ancient times. Many essential oils contain isoprenoids. Some, such as oil of wintergreen (methyl salicylate) and orange oil (d-limonene), have one predominant component, but most have dozens or hundreds. Trace components impart an oil's characteristic odour, which synthetic or blended oils can rarely duplicate. Essential oils have three primary commercial uses: as odorants in perfumes, soaps, detergents, and other products; as flavours in baked goods, candies, soft drinks, and many other foods; and as pharmaceuticals, in dental products and many medicines (seearomatherapy).