What are narcotics?

Narcotics are primarily defined as drugs that can relieve pain and induce sleep, but the term is often associated with substances that have a high potential for abuse and addiction. This includes illegal drugs such as heroin, as well as controlled substances that are misused. The correct choice accurately captures this definition by indicating that narcotics include illegal or unlawfully possessed drugs, which encompasses a range of substances that are regulated due to their potential for harm and abuse.

This definition aligns with the legal and medical context in which the term "narcotics" is used, highlighting not only the illicit nature of some substances but also the broad implications for public health and safety. In contrast, the other options describe categories of substances that either fall outside the scope of narcotics, such as commonly prescribed medications, natural substances used in traditional medicine, or over-the-counter pain relievers, which typically do not have the same legal ramifications or abuse potential associated with narcotics.