A chemical molecule consisting of carbon and hydrogen atoms bonded in a chainlike structure; combined through its acid group (-cooh) with the alcohol glycerol to form triglycerides. They are carboxylic acids with long hydrocarbon side chains that may or may not contain carboncarbon double bonds. Most naturally occurring fatty acids have an even number of carbon atoms because they are synthesized from 2-carbon units. Fatty acids rarely have less that 14 or more than 20 carbon atoms in biological systems. Fatty acids are rarely 'free.' they most frequently occur as esterified components of other saponifiable lipids. Some fatty acids are essential, that is, our bodies cannot make them, therefore we have to eat them. The two essential fatty acids in humans are linoleic and linolenic acid. Butter contains a wide variety of fatty acids that contribute to its functional advantages and characteristics. The presence of short-chain fatty acids contributes to butter's quality as a softer fat.