The name 'glycereth- is used to describe a PEG (polyethylene glycol) ester of glycerol. The number after the name "glycereth-" indicates the average number of molecular units (-CH2-CH2-O-), e.g. glycereth-5, glycereth-7, glycereth-31, etc. The consistency (liquid to solid) and chemical-physical properties of the glycereth-derivative depend on the respective number of molecular units.
In cosmetic applications the esters of different carboxylic acids with the different PEG derivatives are used as emulsifiers, surfactants, emulsion stabilizers.