Is there a name for words whose meaning can be 'reversed' by adding a prefix?

What I mean is words like unlikely, impossible, dissimilarity , which include a prefix that causes the meaning to be exactly the opposite of the original word. Do these words have a particular name?

Are there any rules as to what prefix, e.g "dis-", "un-", "im-", etc. is used for which word?


  • 'Antonym' is another in this group. I don't know of a special name for this group of antonyms. However, greek roots are more likely to have a greek negative prefix (anti- dys- ); latin ( in- > impossible; dis-, non-); germanic (un-). And this rule applies to paired antonyms: upvote, downvote; antenatal, postnatal. – Hugh Mar 24 '19 at 23:24
  • I don’t think there is a single term for such words. They are antonyms, as Hugh says, but so are many non-prefixed words, and antonym only makes sense in relation to something else. They are ‘words derived by adding a negating prefix’, but that’s hardly concise or term-like (though it might work as a better description in your title here). – Janus Bahs Jacquet Mar 24 '19 at 23:47
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    We need two words: profixes (a prefix that intensifies the meaning of the word), and confixes or antifixes. – ab2 Mar 24 '19 at 23:57
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    These affixes are "negators", or negative prefixes. "Are there any rules as to what prefix, e.g "dis-", "un-", "im-", etc. is used for which word?" -- Yes, but it's not that simple. Commonly, the source language of the word decides what prefix goes with it to turn it into an antonym (opposite word). For instance, words derived from Greek and Latin take a prefix different from words originating in Germanic languages. – Kris Mar 25 '19 at 7:03

Your question asks for a term for the words to which a negative prefix can be applied. Google “negative prefix” for more information.

Some prefixes are more likely to be attached to verbs rather than adjectives, etc. as far as I know, there’s no term for words that can be negated with a prefix, although there may be some (like determiners) for which negative prefixes are rare or odd.

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