Antonym is the sense relation that exists between words which are opposite in meaning. Antonyms are a key feature of everyday life. Should further evidence be required, try visiting a public lavatory without checking which the ‘gents’ is and which is the 'ladies.' On your way out, ignore the instructions which tell you whether to 'push' or 'pull' the door. And once outside, pay no attention to whether traffic lights are telling you to 'stop' or 'go.' At best, you will end up looking very foolish; at worst, you will end up dead.
“Antonyms hold a place in society which other sense relations simply do not occupy. Whether or not there exists a 'general human tendency to categorize experience in terms of dichotomous contrast' is not easily gauged, but, either way, our exposure to antonyms is immeasurable: we memorize 'opposites' in childhood, encounter them throughout our daily lives, and possibly even use antonyms as a cognitive device to organize human experience." (Steven Jones, Antonyms: A Corpus-Based Perspective. Routledge, 2002)
Antonyms are a kind of very useful semantic relation. Antonym pairs are used in a large number of idioms and proverbs in English. Whether in common speech or in literary writing, antonym is often employed to achieve rhetorical effects, in fact, it is even indispensable in such figures of speech as oxymoron, paradox, and irony. Furthermore, antonyms also have its remarkable significance in language teaching and learning. It is commonly used in folk definitions, i.e. a thing or quality can often be defined in terms of what it is not, for example, big can be defined as “not small”. When teaching their children or students new words, parents and teachers often resort to this means. Lexicographers often do the same thing in defining a word in their dictionaries. In fact, antonym, as Jackson (1988) notes, ranks the second (only next to synonymy),