What do you call a word that has the opposite meaning of another word?

The term that describes a word with the opposite meaning of another word is "antonym." Antonyms are pairs of words that convey opposite concepts; for example, "hot" and "cold" or "happy" and "sad." Understanding antonyms is essential for enhancing vocabulary and comprehension in reading and writing, as it allows one to grasp the full spectrum of meanings and nuances within language.

The other terms listed refer to different concepts: "synonym" denotes words that have similar meanings, "contronym" refers to a word that can have opposite meanings depending on context (like "cleave" which means both to adhere and to cut), and "homonym" means words that sound the same or are spelled the same but have different meanings (such as "bat," referring to a flying animal or a piece of sports equipment). Each of these other terms plays a unique role in language but does not fit the definition of a word that is opposite in meaning.