A word meaning the opposite of another word, such as “hot” and “cold,” is called an antonym. The relationship between two such words is known as antonymy. “Hot” and “cold” are often described as gradable antonyms because they occupy opposite ends of a temperature scale, with intermediate possibilities such as warm and cool.
Not every opposite pair works in exactly the same way. Complementary antonyms form a more absolute contrast, as with “odd” and “even,” where something ordinarily belongs to one category or the other. Relational antonyms describe the same relationship from opposing viewpoints: “teacher” and “student,” or “buy” and “sell.”
Antonym is often used broadly as a synonym for “opposite,” but some linguists use the term more narrowly. The word comes from Greek roots meaning “opposite” and “name.” Antonyms should not be confused with synonyms, which have similar meanings, or homophones, which sound alike but may differ in meaning and spelling. A single word can also have more than one antonym depending on its sense: “light” may oppose “heavy” or “dark.”