【Drug】 , 【medicinal】 , 【pharmaceutical】 , 【biologic】 , 【simple】  are comparable when they denote a substance used by itself or in a mixture with other substances for the treatment of or in the diagnosis of disease.

【Drug】 is the ordinary comprehensive term in both general and professional use for such a substance, whether of plant, animal, or mineral origin, or produced synthetically, and in its broadest use denotes any substance used as a medicine or in making medicines.

Especially in technical use the term also has certain more specific uses; sometimes it may denote a 【medicinal】 substance recognized in an official pharmacopoeia or formulary as distinguished from one used in folk medicine or proprietary remedies; even more specifically it may denote a narcotic and especially an addictive narcotic substance.

【Medicinal】  is interchangeable with 【drug】 in the latter’s comprehensive sense and is often preferred, especially in commerce, in manufacture, and in law where indication of the ultimate use of the substance is for one reason or another desirablex.

【Pharmaceutical】 is also often preferred to  【drug】 by pharmacists and manufacturers, especially as a designation of drugs (as quinine, cod-liver oil, and aspirin) which are commercially refined or prepared or synthetically manufactured. The term is also used to distinguish strictly therapeutic substances from other substances of similar origin or composition.

【Biologic】  is the increasingly frequent designation for a therapeutic product (as a globulin, serum, vaccine, or antibody) that is ultimately a product of living organisms.

【Simple】 usually denotes a plant product used for its real or fancied 【medicinal】 value especially in primitive or folk medicine. It may also be used of a plant 【drug】 or 【medicinal】 preparation containing only one active ingredient.