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-7, glycereth-12, 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 (e.g. esters of coconut fatty acid as glycereth cocoate)