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1896, from ion + -ize. Related: Ionized; ionizing.
ionize i·on·ize (ī'ə-nīz')v. i·on·ized, i·on·iz·ing, i·on·iz·es To dissociate atoms or molecules into electrically charged atoms or radicals.
To give an atom or group of atoms a net electric charge by adding or removing one or more electrons.
To form ions in a substance. Lightning ionizes air, for example.