Antonym

Is a word that has the exact opposite meaning of another word. Most antonyms are pretty obvious, like "good" and "bad," or "black" and "white." Some words can be transformed into their antonyms simply by adding the prefixes "un," "in," or "non," as when "likable" is changed into its antonym, "unlikable." The word antonym itself takes the Greek word anti, meaning "opposite," and adds it to -onym, which comes from the Greek onoma, or "name." So antonym literally means "opposite-name."