- Any substance that is liquid at ambient temperatures and does not mix with water.
- May mix with other oils and organic solvents.
- Can be produced in remarkable diversity by plants, animals, and other organisms through natural metabolic processes. (organic oils)
- Can also be made from ancient fossilized organic materials such as zooplankton and algae. (mineral oils)
- Oil is used for cosmetics, religion, paintings, heat transfer, lubrication, fuel, and chemical feedstock.