noun

• (organic chemistry) A class of tetraterpene plant pigments; they vary in colour from yellow, through orange to red, this colour originating in a chain of alternating single and double bonds.
• (organic chemistry) Specifically, a number of isomers of tetraterpene hydrocarbons, C₄₀H₅₆, (especially beta-carotene), present in carrots etc, which are converted into vitamin A in the liver.