antonym

A word that has the exact opposite meaning of another word is its antonym. Life is full of antonyms, from the "stop" and "go" of a traffic signal to side-by-side restroom doors labeled "men" and "women."

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."

Definitions of antonym
1

n a word that expresses a meaning opposed to the meaning of another word, in which case the two words are antonyms of each other

“to him the antonym of `gay' was `depressed'”
Synonyms:
opposite, opposite word
Antonyms:
equivalent word, synonym
two words that can be interchanged in a context are said to be synonymous relative to that context
Types:
direct antonym
antonyms that are commonly associated (e.g., `wet' and `dry')
indirect antonym
antonyms whose opposition is mediated (e.g., the antonymy of `wet' and `parched' is mediated by the similarity of `parched' to `dry')
Type of:
word
a unit of language that native speakers can identify