A more thorough explanation:

Definition: Fair warning is a legal requirement that a criminal law must clearly define an offense so that a reasonable person can understand what conduct is prohibited. It also means that a skilled lawyer should be able to predict what conduct falls within the scope of the law.

Example: Let's say there is a law that prohibits "reckless driving." This law is not clear enough because it does not define what "reckless driving" means. A person may not know what actions are considered reckless driving, and a lawyer may not be able to predict what conduct falls within the scope of the law. Therefore, this law does not provide fair warning.

Another example: A law that prohibits "theft" is clear enough because it defines the offense. A reasonable person can understand that taking someone else's property without permission is theft, and a lawyer can predict what conduct falls within the scope of the law. Therefore, this law provides fair warning.

The examples illustrate the definition of fair warning by showing how a law can be too vague or too broad. A law that is too vague does not provide fair warning because people may not know what actions are prohibited. A law that is too broad does not provide fair warning because it may cover too many actions, making it difficult for people to know what conduct is prohibited.