Butyric acid (from Greek βούτῡρον, meaning "butter"), also known under the systematic name butanoic acid, abbreviated BTA, is a carboxylic acid with the structural formula CH₃CH₂CH₂-COOH. Salts and esters of butyric acid are known as butyrates or butanoates. Butyric acid is found in milk, especially goat, sheep and buffalo milk, butter, parmesan cheese, and as a product of anaerobic fermentation (including in the colon and as body odor). It has an unpleasant smell and acrid taste, with a sweetish aftertaste similar to ether. It can be detected by mammals with good scent detection abilities such as dogs at 10 parts per billion, whereas humans can detect it in concentrations above 10 parts per million.