An ELT Glossary : Antonyms
Definition : Words which are in some way "opposite" to or incompatible with each other (ie if something is X, it can't also be Y). They may belong to various word classes - eg adjectives (rich-poor), adverbs (quickly-slowly) verbs (push-pull, pack-unpack), nouns (Sunday, Monday). They can be divided into gradable/ungradable antonyms, converse antonyms and complementary antonyms.
Click on the links for definitions, examples and further information for each type.