Antonyms
An antonym is one of a pair of words with opposite meanings. Each word in the pair is the antithesis of the other. A word may have more than one antonym. There are three categories of antonyms identified by the nature of the relationship between the opposed meanings. Where the two words have definitions that lie on a continuous spectrum of meaning, they are gradable antonyms. Where the meanings do not lie on a continuous spectrum and the words have no other lexical relationship, they are complementary antonyms. Where the two meanings are opposite only within the context of their relationship, they are relational antonyms.
Read more about this topic: Opposite (semantics)