Any of a diverse group of organic compounds that are grouped together because they do not interact appreciably with water. One of the three large classes of substances in foods and living cells, lipids contain more than twice as much energy (calories) per unit of weight as the other two (proteins and carbohydrates). They include the fats and edible oils (e.g., butter, olive oil, corn oil), which are primarily triglycerides; phospholipids (e.g., lecithin), which are important in cell structure and metabolism; waxes of animal or plant origin; and sphingolipids, complex substances found in various tissues of the brain and nervous system. Since insolubility is the defining characteristic, cholesterol and related steroids, carotenoids (see carotene), prostaglandins, and various other compounds are also classifiable as lipids.

This entry comes from Encyclopædia Britannica Concise.
For the full entry on lipid, visit

Seen & Heard

What made you look up lipid? Please tell us what you were reading, watching or discussing that led you here.