Polyunsaturated fatty acids are named several ways. The omega system of naming fatty acids is based on the first double bond from the end of the carbon chain. If the first carbon-carbon double bond is located at the third double bond, then it is an omega-3 fatty acid. One example of an omega-3 fatty acids is the essential fatty acid, . It has carbons and double bonds. It is found in very few foods, including and . The other essential fatty acid is an fatty acid. It has the same number of carbons and has double bonds and is found in a wider variety of foods.