The two major classes of polyunsaturated fatty acids (PUFAs) are the omega-3 and omega-6 fatty acids. Like all fatty acids, PUFAs consist of long chains of carbon atoms with a carboxyl group at one end of the chain and a methyl group at the other. PUFAs are distinguished from saturated and monounsaturated fatty acids by the presence of two or more double bonds between carbons within the fatty acid chain.
Omega-6 fatty acids are a class of poly-unsaturated fatty acids (or PUFA). Other important PUFA classes are omega-3 and omega-9. An example of an omega-6 fatty acid is linoleic acid.
The term "omega-6" refers to the location of the first double carbon bond in the fatty acid chain. The letter omega is the last letter in the greek alphabet and designates "last" or "the end." In omega-6s the first double bond between carbon atoms is located 6 carbon atoms away from the tail (=omega) end of the chain. In omega-3s this double bond is located 3 carbon atoms removed from the tail end of the the fatty acid chain.
