What is a substance called that is taken into the body to treat or prevent a disease?

The term 'drug' refers specifically to any substance that, when introduced into the body, has a physiological effect, often used for treatment or prevention of diseases. This encompasses various forms of medications and substances used in medical practice. The importance of understanding this terminology lies in its broad application, covering anything from over-the-counter medications to prescription treatments.

While 'medicine' is often used interchangeably with 'drug,' it generally refers to substances specifically formulated and dispensed for use as treatment for ailments. 'Compound' typically denotes a chemical substance made up of two or more elements and is not confined solely to the context of medicinal use. 'Therapeutic agent' is a broader category that includes any substance used in treatment but does not specifically capture the understanding of a 'drug' in a clinical sense. Thus, calling it a drug emphasizes the function of the substance in treating or preventing disease.