An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetherolea, or simply as the oil of the plant from which they were extracted, such as oil of clove. An essential oil is "essential" in the sense that it contains the "essence of" the plant's fragrance—the characteristic fragrance of the plant from which it is derived. The term "essential" used here does not mean indispensable or usable by the human body, as with the terms essential amino acid or essential fatty acid, which are so called because they are nutritionally required by a given living organism.
Essential oils are generally extracted by distillation, often by using steam. Other processes include expression, solvent extraction, sfumatura, absolute oil extraction, resin tapping, wax embedding, and cold pressing. They are used in perfumes, cosmetics, soaps and other products, for flavoring food and drink, and for adding scents to incense and household cleaning products.
Essential oils are often used for aromatherapy, a form of alternative medicine in which healing effects are ascribed to aromatic compounds. Aromatherapy may be useful to induce relaxation, but there is not sufficient evidence that essential oils can effectively treat any condition. Improper use of essential oils may cause harm including allergic reactions and skin irritation, and children may be particularly susceptible to the toxic effects of improper use.
In general use, herbs are plants with savory or aromatic properties that are used for flavoring and garnishing food, medicinal purposes, or for fragrances.
A condiment is a spice, sauce, or preparation (such as onions) that is added to food, typically after cooking, to impart a specific flavor, to enhance the flavor, or to complement the dish. A table condiment or table sauce is more specifically a condiment that is served separately from the food and is added to taste by the diner.
Condiments are sometimes added prior to serving, for example, in a sandwich made with ketchup, mustard or mayonnaise. Some condiments are used during cooking to add flavor or texture: barbecue sauce, compound butter, teriyaki sauce, soy sauce, and marmite and sour cream are examples.
Many condiments, such as mustard or ketchup, are available in single-serving packets, commonly when supplied with take-out or fast-food meals.