A Drug is a substance which causes a psychological and / or physiological effect after consumption, which is not a food.
This term can encompass various compounds, chemicals, supplements, medicines, remedies, narcotics, and even plants, ranging from relatively benign drugs like coffee, chocolate, and tea, to highly addictive drugs like cigarettes and heroin.
Drugs can be stimulating (amphetamines, methamphetamine, cocaine) sedating (gamma hydroxybutyrate, diazepam) hallucinogenic (psilocybin mushrooms, tabernanthe iboga, DMT) or have combinations of these and more psychological effects, such as alcohol which can be both stimulating and sedating, or marijuana which can have all three aforementioned effects. Some drugs have primarily physiological effects such as viagra, and other drugs have virtually exclusively psychological effects as in the case of some nootropics.
A drug can have significant health risks, like alcohol, cigarette and methamphetamine, but can also be without significant health risks in moderate doses like caffeine or psilocybe mushrooms.
A drug can be highly addictive, such as in the case of heroin, or can have little to no potential for addiction, such as LSD.