First attested in English 1176, the word oil comes from Old French oile, from Latin oleum, which in turn comes from the Greek ἔλαιον (elaion), "olive oil, oil" and that from ἐλαία (elaia), "olive tree", "olive fruit". The earliest attested forms of the word are the Mycenaean Greek 𐀁𐀨𐀺, e-ra-wo and , e-rai-wo, written in the Linear B syllabic script.
Organic oils are produced in remarkable diversity by plants, animals, and other organisms through natural proteins, waxes and alkaloids.
Lipids can be classified by the way that they are made by an organism, their chemical structure and their limited nonpolar molecules, but may include both polar and nonpolar regions as in the case of phospholipids and steroids.
Crude oil, or Mineral oil also refers to several specific distillates of crude oil.
Given that they are non-polar, oils do not easily adhere to other substances. This makes them useful as lubricants for various engineering purposes. Mineral oils are more commonly used as machine lubricants than biological oils are. Whale oil is preferred for lubricating clocks, because it does not evaporate, leaving dust, although its use was banned in 1980. As no suitable substitute is available, whale oil is still used in space (in small quantities).
Some oils burn in liquid or aerosol form, generating light, and heat which can be used directly or converted into other forms of energy such as electricity or mechanical work. To obtain many fuel oils, crude oil is pumped from the ground and is shipped via oil tanker or a pipeline to an oil refinery. There, it is converted from crude oil to diesel fuel (petrodiesel), ethane (and other short-chain alkanes), fuel oils (heaviest of commercial fuels, used in ships/furnaces), gasoline (petrol), jet fuel, kerosene, benzene (historically), and liquefied petroleum gas. A 42 gallon barrel (U.S.) of crude oil produces approximately 10 gallons of diesel, 4 gallons of jet fuel, 19 gallons of gasoline, 7 gallons of other products, 3 gallons split between heavy fuel oil and liquified petroleum gases, and 2 gallons of heating oil. The total production of a barrel of crude into various products results in an increase to 45 gallons. Not all oils used as fuels are mineral oils, see biodiesel and vegetable oil fuel.
^ . Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
^ in Liddell and Scott.
^ "Oldest Oil Paintings Found in Afghanistan", Rosella Lorenzi, Discovery News. Feb. 19, 2008.
^ Troubled waters: Did we really save the whale?