Main Entry: ion

Pronunciation: \ˈī-ən, ˈī-ˌän\

Function: noun

Etymology: Greek, neuter of iōn, present participle of ienai to go — more at issue

Date: circa 1834

1 : an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons
2 : a charged subatomic particle (as a free electron)