In a narrow sense, wax usually refers to fatty acids, monovalence or bivalence aliphatic fatty alcohol and oiliness substance with higher melting point. In a broad sense, it normally refers to grease substances with similar characters. On various occasions, the definition of wax is different. But in a broad sense, the wax usually refers to a flammable, insoluble-in-water & some lubricating function material produced by plants, animals or minerals, which is the solid at normal temperature but an easily liquefying or gasifying substance after being heated. Macromolecule monohydric alcohol and long chain fatty acid form ester, which differs from the fat & polyether wax in the chemical structure. So, it is called ester wax. Wax is an insoluble-in-water solid. Which will become soft at high temperature and while stiffen at low temperature. Its biological function is as organism’s protection layer from outside environment, existing in skin, fur, feathers and plant leaves, fruit as well as on the surface of many insects’ exoskeleton.

Long chain fatty acid ester of macromolecule monohydric alcohol is called real wax, such as the main constituent of beeswax is long chain monohydric alcohol (C26~C36) cetylate; lanocerin is a complicated mixture containing ester wax, alcohol and fatty acid and purified lanocerin is called lanolin which is the fatty acid ester of lanosterol; carnauba wax is an important vegetable wax and a mixture of ester wax with the chemical formula of CH3(CH2)nCOO(CH2)n+1CH3, n＝22～32.
The congealing point of wax is as higher as 38~90℃. Lower iodine (1~15) value means the degree of unsaturation is lower than that of neutral fat.