The two major classes of polyunsaturated fatty acids (PUFAs) are the omega-3 and omega-6 fatty acids. The difference between omega-6 and omega-3 fatty acids is based on the location of the first double bond, counting from the methyl end of the fatty acid. Omega-6 fatty acids (ω-6 fatty acids) have a final carbon-carbon double bond in the n-6 position.