- a colorless, odorless, crystalline, slightly water-soluble solid, C4H4O4, isomeric with maleic acid, essential to cellular respiration in most eukaryotic organisms: used in the making of synthetic resins and as a replacement for tartaric acid in beverages and baking powders.
- a colourless crystalline acid with a fruity taste, found in some plants and manufactured from benzene; trans -butenedioic acid: used esp in synthetic resins. Formula: HCOOCH:CHCOOH
