A 2-hydroxydicarboxylic acid that is succinic acid in which one of the hydrogens attached to a carbon is replaced by a hydroxy group. ChEBI: Malic acid is a 2-hydroxydicarboxylic acid that is succinic acid in which one of the hydrogens attached to a carbon is replaced by a hydroxy group. It has a role as a food acidity regulator and a fundamental metabolite. It is a 2-hydroxydicarboxylic acid and a C4-dicarboxylic acid. It is functionally related to a succinic acid. It is a conjugate acid of a malate(2-) and a malate.