The term for a word that has the opposite meaning is "antonym." Antonyms are used in language to provide contrast and clarify meaning. For example, "hot" is an antonym of "cold," and "happy" is an antonym of "sad." Understanding antonyms is fundamental in building vocabulary and improving language skills, as they help in expressing a wider range of ideas and emotions. Antonyms are often found in dictionaries, providing language learners with various options to enhance their writing and conversation. They are an essential part of semantics, the study of meaning in language.