A more thorough explanation:

Definition: Substance refers to the essential quality or nature of something, rather than its superficial appearance or form. It can also refer to any matter, particularly addictive drugs that can be abused.

• Matter of substance: The substance of a book is its content, not its cover or physical appearance.
• Illegal substance: Cocaine, heroin, and methamphetamine are all examples of illegal substances that can be harmful and addictive.
• Abuse of a substance: When someone uses drugs or alcohol excessively and in a harmful way, it is considered substance abuse.

The examples illustrate how substance can refer to the essential nature of something, as well as to drugs or other matter that can be abused. In each case, the term emphasizes the importance of looking beyond surface appearances to understand the true nature of something.