A biphosphate is any of the following (due to fluctuations in chemical nomenclature over the centuries): One of the two phosphate ions which can be singular to 1 metal ion Monohydrogen phosphate, commonly known as hydrogenphosphate, also known as biphosphate(2-) ([HPO4]2-). Dihydrogen phosphate, also known as biphosphate(1-) ([H2PO4]−). Any salt of phosphoric acid in which only one of the hydrogen atoms has been replaced by a metal ion Calcium biphosphate is monocalcium phosphate Potassium biphosphate is monopotassium phosphate Magnesium biphosphate is monomagnesium phosphate Sodium biphosphate is monosodium phosphate Any diphosphate, which may be: Any pyrophosphate Any simple pyrophosphate salt (which have no hydrogen atoms) Calcium pyrophosphate Tetrasodium pyrophosphate Zinc pyrophosphate Any organic pyrophosphate or any organic molecule with two phosphate groups Adenosine diphosphate Deoxyadenosine diphosphate Cytidine diphosphate Deoxycytidine diphosphate Guanosine diphosphate Deoxyguanosine diphosphate Thiamine pyrophosphate Thymidine diphosphate Uridine diphosphate Any salt or ester with two phosphate groups Hexestrol diphosphate