<p><strong>Noun</strong></p><ul><li>An electrically charged atom or group of atoms formed by the loss or gain of one or more electrons, as a cation (positive ion) or as an anion (negative ion).</li><li>The valence of an ion is equal to the number of electrons lost or gained and is indicated by a plus sign for cations and a minus sign for anions.</li><li>One of the electrically charged particles formed in a gas by electric discharge or the like.</li></ul>