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Essential Oils are any of several chemicals that form the odoriferous essences of a number of plants. In fact an essential oil is any concentrated, hydrophobic liquid containing volatile aroma compounds from plants, which are called aromatic herbs or aromatic plants. They are also known as volatile or ethereal oils, or simply as the "oil of" the plant material from which they were extracted, such as oil of clove. Oil is "essential" in the sense that it carries a distinctive scent, or essence, of the plant. The term essential oil is also applied to similar synthetic substances prepared from coal tar chemicals, and semi synthetic substances prepared from natural essential oils. Essential oils come from the flowers, fruits, leaves, roots, seeds, and bark of many plants. Oil of lavender, for example, is derived from a flower, oil of patchouli from a leaf, and oil of orange from a fruit. The oils are formed in the chlorophyll-bearing parts of the plant, and with plant maturity are transported to other tissues, particularly to the flowering shoots. Whereas the exact function of an essential oil in a plant is unknown, it is supposed that it may be to attract insects for pollination, or to repel harmful insects, or it may be simply a metabolic intermediate. The essential oils are volatile liquids, mostly insoluble in water, but freely soluble in alcohol, ether, and vegetable and mineral oils. They are usually not oily to the touch. They may be grouped into five classes, according to their chemical structure: alcohols, esters, aldehydes, ketones, and lactones and oxides. Essential oils are obtained by one of four methods: steam distillation, extraction by volatile solvents, expression by hand or machine, and enfleurage, a process in which fat is used as a solvent. In modern practice, essential oils, synthesized or obtained from natural sources by any one of the above four methods, are often purified by vacuum distillation. Essential oils are used to impart flavor and delicate aroma to coffee, tea, wines, and distilled liquors. They are the basic ingredients in the manufacture of perfumes, and are also used in soaps, disinfectants, and similar products. Essential oils have an important use in medicine, either for their flavoring qualities or for their pain-relieving and physiological value. They are used in perfumes, cosmetics and bath products, for flavoring food and drink, and for scenting incense and household cleaning products.Various essential oils have been used medicinally at different periods in history. Medical applications proposed by those who sell medicinal oils range from skin treatments to remedies for cancer, and are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown correspondingly more vague, to stay within these regulations. Interest in essential oils has revived in recent decades, with the popularity of aromatherapy, a branch of alternative medicine which claims that the specific aromas carried by essential oils have curative effects. For example, oils are volatilized or diluted in carrier oil and used in massage, or burned as incense. While essential oils do not need, as a group, to have any specific chemical properties in common, beyond conveying characteristic fragrances, they are not to be confused with essential fatty acids.

Organic acids have a carboxyl group and long a chain of carbons attached to it. Fatty Acids, is the common name for a group of organic acids that includes the saturated (hydrogenated), straight-chain acids, with a single carboxyl (COOH) group, that are produced by the hydrolysis of fats, due to which this name has been dubbed. The group also includes all other saturated straight-chain acids and acids with a branched chain or cyclic structure. Formic acid, HCOOH, and acetic acid, CH3COOH, are the simplest fatty acids. Both have sour taste, irritate the skin, and have a sharp smell. Of more complicated structure are butyric, caproic, caprylic, and capric acids, all of which have unpleasant odors. Stearic, palmitic, oleic, and naphthenic acids are greasy materials with little odor.

A growing source of fatty acids is tall oil, a by-product of the pinewood used to make paper pulp. Fatty acids are useful in preparing biodegradable detergents, thickeners for paints, and lubricants. Stearic acid is used to combine rubber with other substances, such as pigments, or materials that control the flexibility of rubber products; it is also used in the polymerization of styrene and butadiene in making artificial rubber. New uses for fatty acids include ore flotation and the manufacture of disinfectants, varnish driers, and heat stabilizers for vinyl resins. Fatty acids are also used in plastic products, such as coatings for wood and metal, and in automobile parts ranging from air-cleaner housings to upholstery.

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