essential amino acid: an amino acid that is required by animals but that they cannot synthesize; must be supplied in the diet
amino acid: organic compounds containing an amino group and a carboxylic acid group
fatty acid: any of a class of aliphatic monocarboxylic acids that form part of a lipid molecule and can be derived from fat by hydrolysis; fatty acids are simple molecules built around a series of carbon atoms linked together in a chain of 12 to 22 carbon atoms