Auto-antonym

An auto-antonym (sometimes spelled autantonym), or contronym (also spelled contranym), is a word with multiple meanings, one of which is defined as the reverse of one of its other meanings. This phenomenon is called enantiosemy,enantionymy or antilogy.

An auto-antonym is alternatively called an antagonym, Janus word (after the Roman god),enantiodrome, self-antonym, antilogy, or addad (Arabic, singular didd).

The terms "autantonym" and "contronym" were coined by Joseph T. Shipley in 1960 and Jack Herring in 1962, respectively. Some pairs of contronyms are true homographs, i.e., distinct words with different etymology which happen to have the same form. For instance cleave "separate" is from Old English clēofan, while cleave "adhere" is from Old English clifian, which was pronounced differently. This is related to false friends, but false friends do not necessarily contradict.

Other contronyms are a form of polysemy, but where a single word acquires different and ultimately opposite senses. For example, sanction — "permit" or "penalize"; bolt (originally from crossbows) — "leave quickly" or "fix"; fast — "moving rapidly" or "unmoving". Many English examples result from nouns being verbed into distinct senses "add <noun> to" and "remove <noun> from"; e.g. dust, seed, stone.

Some contronyms result from differences in national varieties of English. For example, to table a bill means "to put it up for debate" in British English, while it means "to remove it from debate" in American English (where British English would have "shelve").

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