Up and down, short and tall, on and off, open and close, and stop and go are examples of antonym pairs, or opposites. A word has an antonym when it occupies an extreme, such as "hot." Some words do not have antonyms, such as "apple." Learning antonyms is a great way to expand vocabulary because the brain retains more when information is grouped into pairs or sets.
Antonyms do not have to be as simple as "up and down, " and many words have more than one antonym. For example, the opposite of "lazy" is both "energetic" and "industrious." An antonym for "wonderful" is simply "bad" or, with more complexity, "unremarkable."
It is important for a person to learn antonyms to help them better express themselves. Learning antonyms also leads to learning synonyms, and both directly effect the size and complexity of a person's vocabulary. Additionally, antonyms and synonyms help with reading comprehension and fact-retention.
Antonyms can be used to get a better grasp on the meaning of a word. For example, if a person is not sure what the word "humble" means, a dictionary may provide a list of synonyms and antonyms that can help identify the meaning of the word. "Humble" is antonymous with "proud." From this, "humble" means "modest."