A collective name for a group of closely related lipids that contain a chroman-6-ol nucleus substituted at position 2 by a methyl group and by a saturated hydrocarbon chain consisting of three isoprenoid units. They are designated as alpha-, beta-, gamma-, and delta-tocopherol depending on the number and position of additional methyl substituents on the aromatic ring. Tocopherols occur in vegetable oils and vegetable oil products, almost exclusively with R,R,R configuration. Tocotrienols differ from tocopherols only in having three double bonds in the hydrocarbon chain.