An auto-antonym is a word that has two opposite meanings. Antonyms are words that mean the opposite of each other. In an auto-antonym situation, a single word has multiple meanings that are opposites. This kind of word can also be called a contronym.
Although auto-antonyms are identified through specific criteria, there are a surprisingly wide range of words that can be used in different contexts for directly opposite meanings. In order to be an auto-antonym, the two opposite meanings of the word must be represented by a homograph, which means that the word has the same spelling for both meanings. In general, the opposite meanings for auto-antonyms are created through slight nuances in the rhetorical context, which change the meaning from one polar opposite to another.
One example of a common auto-antonym is a word that can be used to mean two opposite things when it is presented as two different parts of speech. For example, a word like “boned” can mean that a meat contains bones, or that it has been processed to remove the bones. Here, the first meaning requires that the word “boned” acts as a conditional adjective in the sentence, where in the second opposite meaning, the adjective is related to a past tense verb form, where a more technical synonym would be “de-boned.”
In other auto-antonym, the word has two different meanings with the same part of speech represented. One example is “weather.” If someone says, “the house weathered the storm well,” the meaning is positive, where an applicable synonym would be, “endured.” If, on the other hand, someone says that, “the house has weathered over the years,” the meaning is generally negative, where the speaker is referencing a weather-beaten or worn condition that is evident. Although in both of these cases, the use of the word “weather” is associated with a verb, in the second case, many speakers may more closely associate it with a passive form, where speakers might say that, “the house has been weathered,” by the elements, not “the house has weathered,” which would imply that the house has had an active part in its own process of decomposition.
A word can become an auto-antonym in a variety of ways. Some auto-antonym words have been gradually interwoven, where two original words came from two different linguistic sources. Some words are simply seen as versatile in a language of common use, or the agreed use of a language by native speakers. Auto-antonyms are just one example of how language is dynamic and changes over time. A closer look at a list of auto-antonyms can help illustrate how these words become designated for double opposite meanings.