Provide examples of antonyms and explain their usage in sentences.

Antonyms are words that have opposite meanings. They are used to express contrast or to convey a different idea or concept. Here are some examples of antonyms and their usage in sentences:

1. Hot - Cold: The weather was scorching hot yesterday, but today it is freezing cold.
2. Happy - Sad: She was happy when she received the good news, but became sad when she heard about the accident.
3. Big - Small: The elephant is big, while the mouse is small.
4. Love - Hate: They used to be best friends, but now they hate each other.
5. Fast - Slow: The car was speeding fast on the highway, but had to slow down in the city.
6. Young - Old: My grandparents are old, while my little sister is still young.
7. Up - Down: He climbed up the stairs and then went down to the basement.
8. Open - Closed: The store is open during the day, but it is closed at night.
9. Beautiful - Ugly: The sunset was beautiful, but the abandoned building was ugly.
10. Buy - Sell: She decided to buy a new dress, but later decided to sell her old one.

These examples demonstrate how antonyms are used to express contrasting ideas or concepts in sentences. They help to provide clarity and emphasize the differences between two opposite meanings.