In Pharmacology, drug is a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being. In federal law, drug is any substance recognized in the official pharmacopoeia or formulary of the nation. It is any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in humans or other animals. Any article, other than food, intended to affect the structure or any function of the body of humans or other animals, is considered drug. Or any substance intended for use as a component of such a drug, but not a device or a part of a device.
Drug is a habit-forming medicinal or illicit substance, esp. a narcotic.
Drugs are chemical substances prepared and sold as pharmaceutical items, either by prescription or over the counter.