In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid, a.k.a. phosphoric acid H3PO4.
The phosphate or orthophosphate ion [PO4] is derived from phosphoric acid by the removal of three protons H. Removal of one proton gives the dihydrogen phosphate ion [H2PO4] while removal of two protons gives the hydrogen phosphate ion [HPO4]. These names are also used for salts of those anions, such as ammonium dihydrogen phosphate and trisodium phosphate.