IPA: /ˌæntəˈnɪmi/
KK: /æn'tɑnəmi/
The relationship between words that have opposite meanings.
In linguistics, antonymy is an important concept for understanding how words relate to each other.
Antonymy is formed from "anti-" (meaning against) and "onym" (from Greek "onuma", meaning name). The term refers to the relationship between words that have opposite meanings, hence names that are against each other.
Think of 'anti-' meaning against and 'onym' relating to names — antonymy describes words that are names with opposite meanings.