Webster's English Dictionary

Enter the word to look up:

ion

ion \'i--*n, 'i--.a:n\ n [Gk, neut. of io-n, pp. of ienai to go - more at 
   ISSUE] 1: an atom or group of atoms that carries a positive or negative 
   electric c harge as a result of having lost or gained one or more electrons 
   2: a free electron or other charged subatomic particle