ionPronunciation: /ˈʌɪən/Translate ion | into German | into Spanish Definition of ion noun an atom or molecule with a net electric charge due to the loss or gain of one or more electrons: [with modifier]:hydrogen ions a sulphate ionSee also cation, anion.Origin: mid 19th century: from Greek, neuter present participle of ienai 'go'ion in other Oxford dictionaries Definition of ion in the US English dictionary
