C5H8NNaO4H2O

monosodium glutamate monosodium glutamate n. The monosodium salt of the natural amino acid L-glutamine ({C5H8NNaO4}), used as a food additive to enhance flavor; abbreviated MSG. It is usually marketed as the monhydrate ({C5H8NNaO4.H2O}). It is commmonly used in Chinese-American restaurants, and has been identified as a main cause of Chinese restaurant syndrome. [WordNet 1.5]