The word oil is derived from the Greek elaia by way of the Latin oleum, both of which mean olive. Olive oil and other clear oils derived from plants have been closely associated with civilization and health for thousands of years. In Genesis a dove brought an olive leaf to Noah as a sign that the biblical flood was over and humans could reinhabit the earth. The Greeks considered the olive tree to be a symbol of victory and purification. Oils have been part of diverse traditions of medical practice in many parts of the world. They have been used to treat wounds and for general care of the body. In addition, oils have been integral to the preparation of foods and fine cuisine. Three types of oil are recognized in the early twenty-first century: vegetable oil, animal oil, and rock oil. Olive oil is a vegetable oil...