Example of antonyms used in the sentence?

A synonym means the same as -- it's another way of saying the same thing. For example, "big" is a synonym for "large." "Fat" is a synonym for "overweight." On the other hand, an antonym is the opposite of the Word-- so the antonym for "big" would be "little"; the antonym for "fat" would be "thin." To use an antonym in a sentence might look like this: "I'm not stupid," he said angrily. "I'm very smart."