‘Lipid’ is the scientific term for fats or oils. Lipids are organic molecules (i.e. carbon-containing molecules derived from living or once living organisms) that are defined by their solubility. They are (relatively) insoluble in water and other ‘polar’ solvents, and soluble in ‘nonpolar’ liquids, such as ether or chloroform. Cholesterol, triglycerides and fatty acids are examples of lipids.