An abbreviation that pops up on a lot of ingredient lists. It stands for EthyleneDiamineTetraacetic Acid and it's a famous molecule for being an excellent chelating agent, i.e. a molecule that can bind to metal ions (coming usually from water) and make them harmless in a cosmetic formula. With a chelating agent, cosmetic formulas stay nice longer.
EDTA is an acid molecule and its salt versions are even more often used, such as the super common Disodium EDTA.