Which term refers to words that have opposite meanings?

The term that refers to words with opposite meanings is "antonyms." Antonyms are important in language because they help to convey contrasting ideas and enhance the richness of communication. For example, "hot" and "cold" or "happy" and "sad" are pairs of antonyms that illustrate this concept. Utilizing antonyms allows speakers and writers to express nuanced meanings and provides clarity in discussions or writings.

The other choices represent different concepts in language but do not convey the meaning of oppositeness. Homonyms relate to words that sound the same but have different meanings, synonyms are words that have similar meanings, and affixes are additional elements added to a root word to alter its meaning. Understanding these distinctions is crucial for effective communication.